Here's what I think so far:
1: you can never have too many Pokemon
2: if you could transfer Pokemon from R/S to D/P, then breeding will be EVER so much more fun!
3: a new Pokemon game means that previously useless Pokemon (such as Sneasel) will have a chance to become finally useful, thanks to new moves, evolutions and such. This means that the metagame will be once again tweaked.
4: All non-GC Pokemon games past Gold and Silver have had infinite replay value for anyone who loves stats (that means me) so this newest game will be no exception.
5: if it's online, then it's going to be spectacular. But so far, Nintendo has only revealed that the wi-fi will be used...I just hope they'll make it online too.
6: it IS going to be spectacular. Nintendo has had a lot of chances to tweak the Pokemon formula for each game. While some people whine about how R/S weren't good, you can't deny that the battle system and metagame are just way better thanks to the natures, berries and other things that Nintendo has done to the game. Stuff the storyline, I play Pokemon simply for the training/battling aspect! I couldn't be bothered what Team Rocket wants to do to the Pokemon, I just want to beat them quickly so I can have access to the breeding cent...I mean, day care.
Things I'd like to see:
1: an evolution of Dunsparce WHOMG!!
2: with the DS's power, Nintendo could make the game much longer and involved to keep those storyline people happy.
3: customisable stuff, like being able to change your trainer's appearance or something
4: roles, like being able to start the game as a cooltrainer or a bug boy.
5: Nintendo needs to bring EV/IV values into the light and show just how complex Pokemon is to all those noobs who don't know anything about advanced play.
6: Tweak the contest system, and give contests a greater part in the game. Make 1 vs 1 contests so that contests can actually be considered a proper part of the game and not just a gimmick. That way, I can use Delcatty and say it's good. (this is most important)
7: more of those nice pathway choice evolutions like Polywrath/Politoed or Bellosom/Vileplume.
8: Some good grass types, some more good bug types, more good bug type moves, more good grass moves, more ghosts and ghost moves, more steel moves...just stuff like that.
9: online play.
10: uh...
yeah. Sadly, this is my most anticipated game at the moment. I'm really showing hardly any intrest in Zelda or even the Wii. (actually, I guess I am anticipating the Wii.)