From the gameplay footage so far it shows Jill being alone so we know at least segments are solo but in other shots we see her with Chris so I would think that it be more like RE0 where they're both solo and together. The only reason I have to believe it won't be co-op at all is the first trailer where you have Jill and Chris pointing a gun at each other threatening to kill the other.
i guess for a tiny hint of co-op was in the first trailer. there was a small scene where both of them reload each other's gun. POSSIBLY a game mechanic for multiplayer, but it's just me depicting every little thing in the video. IMO, i wouldnt mind no co-op, but if there is, i would definitely use it a lot. i did have (a lot) of fun with RE5's co-op, but the being the only person in previous REs is what makes it's atmosphere. it's a win-win for me.