Hmm, here's a tricky one.
I liked Black and White. They were reboots of the series- GameFreak took the opportunity to screw around with some 'traditional' things that fans weren't expecting to change, but these changes were welcome. One of these changes was the whole "There's no old Pokemon in this regional Pokedex" dealio. That was cool, but it got a little old- I know at least I wanted to see some of the older Pokemon in the game at an earlier stage.
Black 2 and White 2 rectified this, big time, adding about.. what was it? 144 older Pokemon to the regional dex? I think that's right. Anyway, that was awesome, a great mix of old and new Pokemon before the Elite 4, that was great.
However, I'm not anticipating a regional dex of the same size as Black 2 and White 2. The only reason it was so large was to show that, in the years that passed since Black and White, some Pokemon migrated bit by bit across the region. That, and if B2W2's regional dex consisted solely of Unova Pokemon once again, do you really think people would've been interested in it?
For X and Y, I think a regional dex of about 200 would be pretty nice, like with Platinum (which had 210). I'm hoping there'll just be about 100 new Pokemon overall, because.. well, that's just what I'd like. I think it's hugely unlikely that there'll be ANOTHER 150+ new Pokemon. I think that was just part of the 'reboot' factor Black and White had. While X and Y are the first main-series games on 3DS and that's a big deal, I've a feeling we can consider them as the Gold/Silver to Black(2) and White(2), in terms of the amount of Pokemon that will be introduced and stuff.
