Bioware could make ME on the PS3, but not at the moment.

[Saiyar]

http://forums.bioware.com/forums/viewtopic.html?topic=607257&forum=22&sp=9

"Sorry folks, this is just another rumor at this stage. *Could* BioWare make Mass Effect for the PS3 (or the PC, or some other platform) in the future? Yes we could, but we are not working on a PS3 version currently."

So, no version in developement or planned in the near future but at least the confusion over who owns the rights between, MS or EA has been cleared up.