Since apparently telling people not to put all their speculation eggs in one basket doesn't work, let's see some theories!
1) MORE TYPES: No. After GSC, no more types are necisary, those were only put in as a balancing effect. But not just for psychic: Dragon got attacks better than Dragon Rage in GSC, and in RBY, no types resisted them (because they hit for fixed damage). So it would make sense that Nintendo wouldn't add any more types: no more balance is needed.
2) MORE ATTACKS:
Salamence: DD/Outrage/Draco Meteor/Earthquake/Fire Blast/Aqua Tail.
Starmie: Rapid Spin/Hydro Pump/Thunderbolt/Ice Beam/Surf/Recover.
Scizor: Bullet Punch/U-turn/Bug Bite/Superpower/Pursuit/Quick Attack or Areal Ace.
Lucario: SD/Extreemspeed/Close Combat/Crunch/Ice Punch/Bullet Punch.
Yeah right.
3) MORE PER TEAM: Not a chance. Personally, I'd prefer an ingame function that also sticks 2 HM slaves that can't battle or be switched into the main team (unless you're at the PC) in your party, but for competitive purposes? Why change it?
4) NO PHYSICAL BLISSEY: Anyone else notice that Blissey is on the decline now? It would certainly help counter something if a physical Blissey existed... but it would have to be normal, and not something like Steel/Flying.
5) FOURTH GEN DESIGNS SUCKED!: Oh yeah, a ball of gas called Gastly is UBER IMAGINATIVE, but a freaking moai statue with an epic moustache is descusting. (btw, put a monocle on a probopass sprite. It'll change your views of it forever)
6) EVOLUTIONS IN GEN 4 ALL SUCKED: Yeah, you try using Rhydon or Magnaton in OU as apposed to Rhyperior or Magnazone. Tell me how that works out. The only different one is Pory2 and Z, but those are different... 2 is for anti-metagame purposes, and Z is for sweeping.
Now for some of my own!
- Pokemon destined to be jokes (Un-own, Luvdisk, Shuckle, maybe Farfy.) won't evolve. Hopefully, Magcargo will though, and FINALLY GET SOLID ROCK. Also, Absol and Torkoal maybe.
- A phisical electric attack that doesn't require a fist to use will come out. Luxray fans rejoice.
- Same with fire. Flareon and Entei get a lot of speculation because of them.
- Phsical hidden power. What, they pulled out a special Choice Band the gen after it came out!
- One pokemon will be claimed as "Completely broken", and turn out not to be (Early DP Garchomp anyone? Well, until the Yache berry incedent it wasn't).
- Garchomp and possibly SDless Latios will become OU.
- The early Normal/Flying type will be something like this on the food chain: Staraptor, Swellow, 5th gen, Dodrio, Fearow, Pidgeot, Farfetch'd, Chatot (Togekiss isn't on the list for obvious reasons.) It MIGHT be above Swellow, but I don't think we'll get another Staraptor.
- While everyone talks about "We won't be able to counter everything", a lot of current threats fall out because new pokemon (or old pokemon with enhancements) will rise.
- After Hyper offensive and stalling periods, the metagame will balance.
I think they're good predictions.
EDIT: I KNEW I'd forget one!
- Nintendo's push for the DS-i obseletes GBA games, Hoenn comes back.