Personally I'd rather see a different story if they make another mini game type thing. I liked Lost in Nightmares a lot more than Desperate Escape and I think it has a much higher replay value, especially since the game changes slightly for each difficulty (when you have to unlock the gate that exposes the ladder that ultimately leads to Wesker). I can't say that I would necessarily want to see the same characters again though; I would like a game in which I could play as Rebecca or maybe even as Wesker, outside of Mercenaries.
I'm not sure of the release date :x. But ORC is another reason I don't think they would make a mini game. They've been working on ORC and RE6, and let's face it- I think fans are looking forward to either or both of those than more RE5 DLC.