No, I don't believe that the ME 2 release on PS3 will negatively affect ME 3; I actually think that it's actually positive in that it will let more people enjoy the game.
Even if ME 1 isn't being released on the PS3, there are many ways that you could incorporate the decisions you made in the first game on the PS3 version. One good example is the one listed on the first page of this thread: an interactive flashback that acts as a game save editor, allowing you to create your own Shepard, as well as make the major decisions that occur in the first game (i.e., Feros, Noveria, Virmire, who you romanced, what you did during the ending, etc.). That way PS3 players could get a summary of what occurred in ME 1 and get to make the major choices that affect ME 2 and ME 3.
So no, I don't think that the PS3 getting ME 2 is going to negatively affect ME 3.
