1. "Stop with this 6.5/7.5 nonsense."
Actually, it's not complete nonsense. We have "sort of" gotten .5 gens before. Typically, something I would consider ".5" wouldn't include new pokémone per sé, but they do include some new character models that are not available in the previous iteration of the game. In terms of 6th gen, ORAS had new Megas, which technically are new evolutions. I could see 7th gen sending out a new set of games, either an Alola follow-up or remakes, that give us new Megas or regional formes. Personally, I'm leaning toward the latter. Although we were given "Alola formes" this gen, it doesn't mean that Alola is the only region with unique formes. Technically, we were introduced to "region-based" formes in 4th Gen with Gastrodon. I wouldn't be surprised if some new regional formes popped up in Sinnoh in an area that is remake exclusive. I could see some new area of Sinnoh having regional formes of pokémon from Gen V, VI, or VII since there is no precedent for the normal versions of those pokémon in Sinnoh. We honestly don't know how a Sinnoh Honedge should look, for example, so having a regional variant would be perfectly feasible. It could also be a way to balance the newest gen out in terms of speed. Maybe so many of them are slow because their Sinnoh variant is faster? Who knows?
2. "Last mythical means end of the gen."
Does it? It is possible, since that has been the case before, but as others have stated the distribution of events is typically spread out. Basically, when you get the last mythical, the new gen is on the horizon. Magearna was given out Day 1 (kind of like Victini) and now Marshadow less than a year later. We haven't had a 2 mythical gen since Gen III and those definitely were spread out. So why were these given away so quickly? Moving to the next gen is a possibility. However, the other possibility is that a 7.5 gen isn't so far-fetched. Maybe GF is tired of having their "surprise" event pokémon leaked before the games are even out and have decided to trickle a few out each new game so, even when the full code of a game is released the community still doesn't know every new pokémon of that gen. At this point, I wouldn't be surprised to see a mythical in the next set of remakes that we didn't know about previously. Adding new formes, Megas, and mythicals to remakes actually would make them more worth my money. I was surprised that ORAS had exclusive Megas, and competitively made buying them imperative. Adding new 'mons to a remake certainly makes them all the more viable, both for nostalgia and competition.
3. "But Stars on the Switch, bro!"
Stars was always a rumor and it always surprises me how people latch on to rumors like they are facts... then get disappointed when said rumor turns out to be.. well.. just a rumor. I don't see why a gen would be spread between two different systems and I'm surprised others think this is a good idea. Sure, produce some companion game that allows me to migrate anything I find there to the main games (like Colosseum, XD, or Pokémon Ranger games), but if you're going to produce some new main series game that is in the same gen as one I already own, I don't want to HAVE to also own two systems to play the whole gen.
4. "7th Gen is only going to last a year!"
I would be pretty freaking shocked by this seeing as the anime hasn't even started here in the US yet. I feel The Pokémon Company is going to want to milk this gen dry before moving to the next. Also, we're only about to be 2 - 3 TCG sets in as well. I doubt they'd be rushing their marketing that fast. I could be wrong, but, I mean, we haven't even had a Sun/Moon McDonald's toy run yet. It's be really weird to be moving to gen 8 when they could still be making money on 7th gen.
