I expect R:FoM to still do well on the PS3 for quite some time in the US, and to a lesser extent in Europe.
Realilistically, the only FPS that will come out that has a shot at "stealing" sales from it is Call of Duty 4, as I would put it as one of the few story-driven FPS shooters comparible. There are tons others, but I don't really see how they'll hurt it.
IMO, even though everyone will praise the various other PS3 games out there, both current and upcoming, Resistance has done very, very, very well not only considering the genre, but the software tier ratios as well. The PS3 has around a 2.5 ratio worldwide (this is just my assumption, it's around 1.5 in Japan, and 3.0 in the US). This means that more than 10% of every game sold is Resistance. It should keep selling well throughout the rest of the year. 2m LTD sales worldwide should be a certainty - how much else it sells is unknown to me. A budget re-release could help a bit, or not much (atleast in comparison to the install base).
Back from the dead, I'm afraid.
