I deeply hope that the No Gym thing is true. Time to shake up this universe. But if that would make Synchro evolution and Litten's leaked final stage real... I'd rather stick to the old model.
Like many "leakers" on the internet do, they try to throw in 1-2 fake things in their leaks and I'm pretty sure that gyms will remain in the main series games. I HIGHLY doubt that the core formula of Pokemon itself would just be torn up.
As for Synchro Evolution, I'll admit I was a bit annoyed that they were releasing two mechanics back to back in generations, but now that they've guessed what it does, I'm willing to give it a try. My only concern is that they'd make the 5 move possibility WAY to broken in the meta game...
Finally, Litten's final form isn't that bad. If you look at the Art, it suggests it being Fire/Dark type. This can further be backed up by the fact it's based on a heel wrestler, and likes to "fight dirty". However, in a Pokemon game I really only need to like one starter for me to like them as a set. But I like all three.
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However, these also have a lot more credibility because of their design.
Rowlet evolves in Archer. This makes sense because they are silent while attacking, which lines up perfectly with Rowlet being an Archer. They also have a move called Leafage, which is like shooting a leaf from its plumage, like a dart or an arrow.
Litten evolves into a Wrestler. Sure, you might think of wrestlers as "hot headed" and Litten is pretty much the opposite, but then again, it's also mentioned that Litten has lots of passion. What does wrestling require tons of? Passion.
Popplio's story is kind of, "be careful who you call ugly in middle school". Popplio is already seen as dorky, and clown like. As a result, the Pokemon community doesn't really like Popplio, and give tons of phrase to Rowlet (sets up flame shield) who really isn't as great as people think he is. Popplio goes from being the odd looking sea lion (or seal or whatever) to this goddess of a Pokemon, which is something truly beautiful, and an amazing concept for Pokemon to involve. Also, the Pokemon looks amazing, and if these leaks are real, I'm choosing Popplio all the way.
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Then there are other aspects of this, a sea cucumber, dolphin, and rugby monkey all sound like different things that I don't really recognize (unless I'm being stupid and Mankey is a rugby monkey, sorry I'm tired) in the Pokemon world. I'm not sure Id catch any of those Pokemon, as none of them really appeal to me much. But, I'm sure for all those people who've been CLAMORING for a dolphin for years, you'll love that.