Blizzard will not release both Starcraft 2 and Diablo 3 the same year.
They have never released 2 big games the same year in the past and financially they will want to delay one to 2010 anyway( even without a voluntary delay I highly doubt D3 would be ready in 2009 anyway, it's Blizzard, they will not rush something that they think is not ready)..
My understanding is that Starcraft 2 development is more advanced so that will be the Blizzard game released in 2009 but you can remove Diablo 3 from your list.
It will be the top rpg of 2010 ( ahead of FFXIII I am pretty sure, the Diablo serie keeps picking up new fans while the FF one is no longer at its peak based on the sales of the last 3..). D3 will benefit from the fact that the competition on PC is nill too, so every PC gamer will pretty much buy it...( 7 years after D2 release Blizzard just had to release the first information about D3 and D2 battlechest shot up to the top 5 pc game sales the following week...).
PS3-Xbox360 gap : 1.5 millions and going up in PS3 favor !
PS3-Wii gap : 20 millions and going down !
