To be honest, I'm not expecting an Uncharted 4 from Naughty Dog. At all.
Naughty Dog transitions to a new IP every gen. Crash Bandicoot was PS1, then they shifted gears to Jak & Daxter for PS2, then Uncharted for PS3. The Last of Us, yes, I would definitely expect a sequel to that on PS4, since that seems very much like their new IP for next gen. But no Uncharted 4. I think they're done with the series. History says so.