A little bit of sitrep with a complete lack of sources because I can't be assed to look for any. Either trust my word on these or google, this whole thread is purely for speculation anyway. Ahem...
So, a while ago Capcom revealed that they are making a new game with the RE Engine (that is not RE3, RE8, Resistance or the upcoming unannounced RE title) and they've been pretty coy about it since. Speculation only grew when they revealed this was not going to be a new IP but something regarding an old series of theirs. A little later a trustworthy leaker said it was going to be a "reboot" of sorts (something akin to what RE experienced), meaning it could be a remake, a soft reboot or a complete reboot of one of their old franchises. Now, since this was the RE Engine speculation focused mostly on Dino Crisis, as it would be the next best contender for any of those options using the engine. However, the same leaker again went on record to say that this was NOT a Dino Crisis game. So... What the heck could it be? That's what we're speculating here today!
What do you think it could be? Capcom has a ridiculous catalogue of games (so many that even Wikipedia has to seperate them on different pages per letter) and honestly it could be anything. I doubt it'd have anything to do with Devil May Cry since they just remastered the old titles for current gen and made DMC5 to great acclaim, nor do I think it's Monster Hunter as they are still milking World. After that we can pretty much rule out any sidescrolling games, including fighting games like Street Fighter, because it would be a ridiculous task to convert the RE Engine for something like that, not to mention completely useless as I'm sure they have way better engines for games like that. Plus, you know, the fighting game competitive scene is still very alive with SF5 and it's still getting DLC. With what we have left, not counting any one-offs, I personally think that it's either Onimusha, Lost Planet or Dead Rising.