Anyone have any idea what they will be? 

No idea, but I'm hoping Blizzard will do what they have in the past and release it for Mac as well as PC.

From the visuals of the last trailers i would say it will easily run on maximum with an 3 or 4 years old PC. (OFC without DX10 Support.)

Keep in mind this game likely isn't coming out until 2011. So at this point trying to speculate on specs for a PC game that isn't coming out for a couple of years is kind of moot.

I'm guessing it's going to require:
Optimal performance:

a current high end dx10 video card,
6-8 GB ram
Quad core processor or i7
140 GBs

recommended
4 GB ram
Dual core processor
maybe something slightly better than a 512 9800XT
140GBs

Joke post?

I think the Collector's Edition will need 200GB for the Pokemon anime movies they will include

how is that a joke starcraft? because blizzard is known to release software that runs on most computers? Let me remind you that the recommended reqs I said are about 3 years old now, and on release may be 4-5 years old.

all that stuff can be upgraded to within a hundred-two hundred dollars now.

theproof00 : but from screens DIII doesn´t look that demanding. And what´s with this "140 GB"?

fyi starcraft, this is the reqs for sc2
GFX: GeForce 7/8 Series or Radeon 1000/2000 with 256 MB RAM
CPU: Pentium 4
RAM: 1 GB
Internet: ADSL 1 Mbit

Recommended Requirements
GFX: GeForce 8000 or Radeon 2000 series with 512 MB RAM
CPU: Core 2 Duo or Athlon X2.
RAM: 2 GB
Internet: ADSL 3 Mbit

Optimal Requirements
GFX: Geforce 9000er or Radeon 3000er Series
CPU: Core 2 Duo 3 GHz or Athlon X2
RAM: 2GB with DualChannel mode

For Diablo 3 which will probably come out 1-2 years after sc2, my reqs were pretty good.