Yes, yes they can. Because they've been around for aaaaaaaaaaaaaaaggggees anyway.
System shock 1 is the oldest I can think of right now. Next to games like Deus Ex and System Shock 2 the current crop of fps rpg's are actually quite watered down, there's still plenty of space for them to expand.
That they are coming into fashion again now is indicative of player's general lack of interest in the cookie cutter 6-hour fps mould pretty much all major shooters from the last 3 years have filled.
But they certainly ain't a new born genre, not by a long shot.