SecondStoryGamer (linked above) is reporting a 'fairly reliable source' close to EA has told them that the sequel of Mass Effect and future versions in the series will be available on Sony's PS3 as well as the XBox 360 and PC.
Apparently, EA decided to go multi-platform because of the state of the economy, and they want to squeeze as much money as possible out of their games.
To quote: A fairly reliable source close to Electronic Arts tells us that the sequel (and subsequent iterations) will be available the PlayStation 3 as well as the Xbox 360 and PC. According to our source, EA decided to make the series multiplatform mostly due to the "the economic outlook".
Our source claims that because of the current state of the economy, Electronic Arts is looking to squeeze as much money from its portfolio of games as it possibly can. Obviously, making Mass Effect 2 and 3 multiplatform would increase their sales, as the game would be available to more people. More PlayStation 3 News...