Screen Rant reports that Evil Dead 4 is in the works. Apparently Sam Raimi will produce and they're going with an unknown indie director.
The real question is whether Bruce Campbell will reprise his role as Ash - likely not, according to this report. But it also reports that fans want Campbell back and that he may be involved in a cameo role, and they didn't exactly rule out anything.
As for who should play Ash, if not Bruce, my money is on Seann William Scott, who was mentioned when they first started talking about this back in 2004 (incidentally, he is the only other person I have ever heard of who spells his first name the same way I do). But I don't see his name involved anywhere now. The first few scenes of Evolution feature Scott acting very Ash-like, and he's one of those few actors who can handle both "action hero" and "dumbass" in the same role.
But my top choice for Ash was, is, and will always be Bruce. I'm not sure he's in fighting trim these days - on the last few seasons of Burn Notice, he's looked a little chunky. Nothing weird about that in a guy his age (he's 53). But I also noticed on the Season 5 premiere that he's obviously been taking care of himself and slimming down (they even joke about it a bit on the first episode).
Call me a dreamer, but I can only hope he's working out to get into shape to reprise his role as Ash. I guess we'll find out.
As for whether an Evil Dead 4 (which will probably be called something else, and which Raimi is calling a "quasi-remake" of the original Evil Dead) will be a success, I think the whole thing rises or falls on who they cast as Ash. All of those Evil Dead films (1, 2, and Army of Darkness) rely heavily on Campbell's schtick, so whoever wields the shotgun and chainsaw this time around has some very big shoes to fill.