Wow, that's a lot of new info.
New Pokemon: DDR Bird is an interesting concept and I love the design of each one. Then there's Yungoos evolving into Gumshoos, a gumshoe on the stakeout. Oh Gamefreak, you and your puns. The other ones (minior and fomantis) look interesting enough too, and I already loved Mudsdale.
New Forms: Didn't expect this, but it looks like Gamefreak went and made the pokemon variants art meme canon (where artist would draw pokemon with slight breed differences, usually based on egg groups). While it does look pretty cool (see Gamefreak? I can pun too!) I just wonder how they will handle movesets and stats with the alternate forms, or even pokedex entries. And while I welcome any change that keeps the old 'mons in pace with the new 'mons, I hope we don't get a serious case of alternate-itis in the next few generations.
Z-moves: well now I know why the gems from Gen 5 made a disappearance (sans normal gem), since at it's core this is an improved version of the elemental gems. Single use super attacks that require giving up your hold item, yep it's the gems. There are some significant differences though, for one while the gems powered up one of your known moves once this time it gives you an entirely new one to work with. Still lots of questions of course, like:
1. Can you use 6 Z-moves in a battle if you give Z-stones to your entire party?
2. If you have to just know a move of the same type, does this count support moves that aren't attacks? Can a 'mon use the poison Z-move just for knowing toxic for example?
3. Will there be physical and special variants? If there aren't any, then can you use a physical fire attack and still get a special inferno overdrive for example?
4. And general stuff like accuracy and base power. I'm kind of assuming these are just hyper beams without the drawbacks, but they could be more than that.
Still, given the few things we do know, Z-moves will greatly expand movesets for some 'mons that could really just use a better coverage move to use in a pinch, like those that rely on the relatively weak elemental punches and fangs.
No Gyms: I don't mind that they have been taken away, I'm more concerned with what replaces them. Since 4 challenges replacing 8 gyms does sound like getting shorted by the Aloha exchange rate. So for me it's not so much what they took more than it's what they replace it with. It could be great and more involved than gyms ever were... or we could truly be shorted here. I'll wait and see.