I remember the years and years of threads on PokeGym making the same arguments for the game dying. None of what was mentioned in those discussions has ever come to fruition.
Every game had its ups and downs, when I stopped playing the first time, it was during the E-Reader series, and from what I have seen, things SUCKED. And from what I have seen, Pokemon was in a bit of a bad spot before their 20th anniversary and then things began having an uptick.
I do know this much from experience, though: dying can be a very long, slow, and drawn-out affair. The TCG isn't there yet. I don't think it would be the formats or the cards that hurt it. No, I think it could be the players ruining it for themselves.
Up to this point, I haven't seen a game get completely destroyed because the playerbase became so toxic and destroyed it. Look at Yugioh: a game thats known for cheating, expensive cards, and competitively toxic. It's been doing this for years and it's still going, even if it's been having some issues in the last few years.
I don't know every game out there, but if you know of one where the players actually ruined it, I'd like to know as that sounds like an interesting read.
From experience, games that die tend to do so because of bad marketing:
Duel Masters: This was a card game that Wizards of the Coast (WOTC) got the rights to market and distribute in the US in 2004. However, due to lack of marketing, support, and sales, the game died back in 2006. They did make an attempt to try it again and rebranded it "Kaijudo" back in 2014. Again, poor marketing and sales got it canned in 2014. Apparently, it's being doing well in Japan since it's release in 2002. Hasn't had any problems there.
Warball/Warstone: This was made by Duncan, the same people who make Yo-yos. I know, right? They wanted in on some collectable fgame action and they released....competitive marbles. The idea was there, they set up "cities"-esque tournaments and even had a Nationals. But the game died directly afterward. This was was due to, again, marketing and poor sales, and quality control. The symbols on the marbles could be easily rubbed off, which is a no go if you need to shoot them and use them for abilities. Game folded after their Base Set.
Hecatomb: Another WOTC game. This time it was a card game that featured a lot of horror elements with plastic, semi-translucent, pentagon cards. The idea was that when you gave your creatures power ups, you'd overlay them (like evolving) and the power up would be visible through one of the edges, IIRC, you could have something like 5 power ups. The problem here: MARKETING! They aimed this game solely towards a casual player base. I saw this game demoed at a shop and when I had interest in it, it was dead. Died before the release of the second set, but after the set set promo was either spoiled or released, I can't remember.
Dreamblade: This is probably my favorite cancelled game and one of the best CCG games I have ever played because it was HARD. WOTC wanted to cut in on the miniature gaming market and they came out with Dreamblade, an area control game with 25 squares to move around in and 9 of them scored you points. I could go into this game in gross detail all day.
WOTC realized their mistake with Hecatomb by catering to the casual crowd and went in the absolute opposite direction: a game geared solely towards competitive players and M:TG transplants. They outfitted this game with $1K tournaments, $10K tournaments, and a $50K at IndyCon the next year. I loved the game and thought it was doing well, but after it died (it died shortly before Indycon, the $50K happened with every player knowing this would be the last time they'd ever play the game in a competitive capacity), if you looked at the WHY, it made a lot of sense:
- their theme deck was literally a Starter box. This was the only means to get the appropriate map and special dice needed to play. There was nothing enticing for new players to come into the game, even though there were four factions in which they could create stuff with.
- price: Boosters were $14 a pop in 2006-2007. In todays economy, I wouldn't be surprised if it was $17.
- marketing: The game was geared toward an older crowd, which can be problematic.
- release of sets: because $1K tournaments determined the meta, and 5 sets were released within a year, you got whiplash trying to figure the meta out. There WAS a meta, but there was little to no time in trying to make builds that either countered the meta or did anything different, you either ran the meta or you lost to it.
- R&D : Their R&D was really poor, they ended up banning a figure by the time the third set rolled around (Kitsune), but when the 4th set rolled around, a Warband came forth that did what the banned figure did but worse (Kitsune was banned because it encouraged a combo that caused a lot of dwell time to be had on a players turn. It also enabled a lot of damage to be done, but the whole time it took to do it was a process. Anvilborn brought Blademiller builds and the whole combo was even more elaborate).
They also released a Location (Unwishing Well) that was VASTLY overpowered. WOTC did release the stats of the figure they WOULD HAVE released in the 6th set. I can confidently say that Unwishing Well would still be the dominant band to run.
From what I have seen from the successful games, you need to cater to both the CASUAL AND COMPETITIVE players. I know for Yugioh, the sales they get from competitive players is like a drop in the bucket and their sales mostly come from casual players. IT then makes sense that they make their best cards the short print Secret Rares in the set to entice competitive players to buy into boosters and boxes. You need both players to keep the game going: casual to keep the game alive, competitive to essentiall be the "carrot on the stick" for players to work towards.
I'm not sure on Magic, as their demographic is VERY different.
Pokemon is in a really nice spot as it shares the same demographic as Yugioh does and caters to both casual and competitive players. AND they managed to rake in old players like me back in the game during their 20th (seriously, if Imakuni?'s Doduo wasn't printed, I wouldn't be here).
Magic is currently having a lot of issues with their "pro" playerbase. IIRC, it has to do with their moving the goalpost on requirements for their Worlds and less prize support, and that there is little to no way that being "pro" is financially sustainable. I say that because WOTC teases the idea of solely playing M:TG as a way to generate income between sponsorship, prizes from winning events, etc.
This is something that Pokemon HAS NOT and I doubt WILL EVER allude to, and I like them for this. I know some players are able to do this. But encouraging something like this would put Pokemon in a bad spot like what it's currently doing to WOTC.
I gave up on WOTC back in 2007. They messed up a Legacy Grand Prix. Their R&D, in all their benevolence, unerrattaed a dozen cards a few weeks before the event. In the span of 24 hours, people figured out that one of those cards (Flash) anabled a SUPER CONSISTENT one turn kill--even an OTK where the opponent NEVER GOT A TURN IN. It was either run Flash Hulk or you were getting killed by it.
I got fed up with that as well as not having much of any enjoyable experience from M:TG since 2002 and sold my decks, got my money back from booking hotel and flight. Then get killed Dreamblade. And both events happened in less than a year. WOTC did their usual shrug of the shoulder "Sorry we killed a game you liked, we still have M:TG!"--they did this with Pokemon after the E-Reader series too.
I've played a LOT of HEroclix and have nothing but nice things to say about that game. I did play the game from its inception and it went into its dark ages. It kind of stagnated and only got better in 2009.