*DISCLAIMER* This is PURE speculation and nothing more.

So.. we heard for a while that Naughty Dog were targetting 60fps for Uncharted 4. Devs at Naughty Dog were cited saying that TLOU at 30fps felt 'broken' but before that we had the In-engine trailer running at 1080p (constant)60fps.
Then it came down to the demo we got at the PS Experience where it was running at 30fps, the internet cried out for the lack of 60fps but it was mostly people talking about how freaking awesome the game looked. 

BUT later was confirmed that at that moment in time they had uncharted running at about 37fps, which is really good for how amazing it looks and it being a whole year out. During the discovery that it was running at 37fps Neil Druckmann stated that 60fps for Uncharted 4 is "really fucking hard" giving doubt to gamers thinking it will be 1080p 60fps at launch.

NOW fast forward to today we have Naughty Dog delaying Uncharted 4 saying that they are being really ambitious and want to release a fantastic title. Naughty Dog are great at product management they do not release broken games and they don't set release dates without meeting them and producing a solid product. Is it possible that they 'dun goofed up' with their development projections or they believe if they are given another couple of months they can make uncharted 4 60fps?

TL;DR: Naughty Dog are delaying Uncharted 4 for a couple of months to get it to 60fps. Which is what they meant when they said they were being 'ambitious'.

That better be the case. Hopefully The Order taught them something. Set an example, ND.

I hate to break it to you but if it taught them something is that they'll need to settle with 30fps in order to achieve the mainstream perception of next gen visuals.

So, to answer the question, no.

Who knows, MGSV PP is 1080p and 60fps and its open world so this is definitely possible.  Game developers should be begging Kojima to use the Fox Engine, that game being 60fps/1080p, being open world, being one of the best looking next gen games puts it way ahead of what other devs are able to accomplish on the PS4.

It won't run at 60 FPS unless it gets a noticeable visual downgrade.

I doubt it. There would have to be a visual downgrade for that and I just don't see that happening.

But there's already been one. I say it's still possible.

Maybe. I know they said that they were at 37-38 FPS at PSX and they locked it at 30 for the on stage demo. If they really wanted it at 60 FPS, they could easily do it, I just don't know if they want to downgrade the graphics anymore.

You just had to bring up the order.  

Anyway if it ran like it,  we'd all be happy. 

No, "we" wouldn't.