Let's be real: It's going to be a 4.5 hour game again. REmake 2 mitigated that by having two characters, but from the sounds of it they are really stressing Project RE as the way to get your money's worth. I was hoping for RE 7 length (about 9 or 10 hours), but that sounds really optomistic now.
Hm, I don't know why did RE7 took you so long, it's a 6 hours game at most. Resident Evil as always been a series with short games.
And Project RE isn't a way to "mitigate" RE3 length. Hell, I don't see why you would ever think REmake 3 would be long when the original is quite short.