^Gulpin. He's pretty cool.
Anyway, I had typed up a reply way earlier from a different computer, yada yada yada browser issues, and I just couldn't be arsed. So, I'll try it again now from a more reliable computer.
I feel like if anyone is used from previous generations, they'll probably hail from 4 and 5 because it's the most recent, and fresh in the minds of the younger folk, or at least those keeping up with the series. I can't remember any from 2 aside from Spinarak and Ariados, so your guess is as good as mine, there. And from Generation one, I'd only expect Ekans and then Grimer OR Koffing, but not both. Nidos will not be in generation 6, at least not without some kind of trade or import from a different game, because they are not only competing with a thousand other Pokemon or whatever, but they're also criminally unpopular in Japan as it is. That's why I'm not expecting miracles, and make all those posts in jest since I already know it ain't happenin'.
I do see the possibility of Pokes from Gen 3, because I'm certain an R/S remake is inevitable (though unnecessary). All I remember is Gulpin/Swalot and Seviper, though. I could swear G3 had more than that. But seeing Kirlia in the trailer, well, there's at least some G3 Pokemon in there anyway.
As for... what, Froakie? Man, forgot its name already. We were talking about it in class, someone mentioned the possibility that it could be water/ice. That would be pretty interesting. Was Piplup water/ice?
I wouldn't jump to the conclusion that its poison, though, just because it's some kind of frog. It's possible, but there are other options.