Probably not going to happen. If it is not announced at this years E3, (with the current momentum the PS3 has), it will never happen.
Good news is, you being an RPG fan once/if you purchase a 360, you would get access to a large library of RPG's not just Mass Effect. I know many of the 360 RPG's may not appeal to you, but there are a lot to enjoy.
The 360 library is amazing.