*Warning: This is just a rumor. It might change later or have a probablity of being false!

1.Lurker is comming back, but in campaign mode
2.Bunker-infesting creature for zerg
3.You can make multiple motherships, but they're smaller(What's the difference between them and arbiter, then?)
4.Zerg gets devourer, but hav to evolve(Corruptor->Brood Lord->Devourer O_o) Devourer will be massive unit.
5.Terran gets medic back(SC1 version of bionic push might start again O_o)
6.Protoss gets their Dark Archon back >.<
7.Campaign will be based on Kerrigan regaining her power again

4. I love Devourers, though I'm sure a lot of these units are going to be campaign only
5. Medics are toast against banelings, so good.  Medivacs were invented to keep up with reapers, and few people use reapers.  Also, it seems that people get dropships automatically because they need medivacs, and thus it's like "oh, and we've got dropships too.  This will be easy to harass with!"  I really hope medivacs go bye-bye
6. Why? Not many people used Dark Archons except for feedback.  If malestorm has a larger area, that might be something
7. I hope Kerrigan is not going to be infested again.  I keep imagining Zeratul says to Jim, "James, you're supposed to protect her, but she's not supposed to be human" And then Sarah sadly has to force herself to become infested again

I don't think medievacs should disappear, but they should be made much more expensive or require an extra upgrade. Not too much either, though, so people can still do drops.

Actually, I was thinking regular dropships

6. I wonder if mind control will return? I think zerg can do that, right?

Zerg mind control is temporary.  The Dark Archon mind control is permanent.

Also for Zerg, I hope they do something about the late anti-air. In silver league I remember everyone did bancheese and void cheese, so you had to tech to lair asap and get hydras most of the time. X.x

That would be nice, but I don't think it's very likely.  I know how you feel, but most people have not had that kind of problem.  I myself have gotten out of that kind of situation almost 100% of the time

Devourer will be in multiplayer mode
Also, to answer Hot_Dog's question, Kerrigan should be infested again since she regained her conciousness again.
(p.s. Mengsk, your time has come )

More rumors.
8. Devourer WILL have their acid spores
9. HotS will NOT be able to play against WoL. (Aw..)
10: Expected release date is early 2012

Okay, so why use corruptors if devourers come into play

Does corruptors slows down enemy attacks? Also if I remember, devourers were very slow at attacking.

Devourers are slow at attacking, but the acid spores allowed mutalisks to attack with up to 18, 12 and 10 damage on their glave worms, as well as giving hydralisks up to 19 damage.  Corruptors themselves increase damage output by corruption.  So it seems like devourers and corruptors would share roles, except corruptors can take out capital ships themselves.  Devourers are more of a support unit.  Still, thanks to corruptors, I have not needed devourers