PC gamer first and foremost here, but I own almost every modern console except for Xbox One/Wii(U) currently and I'll try to provide my thoughts on this debate.
30 fps is definitely playable, but people that are more used to 60 fps are more likely to notice the difference and it might feel sluggish for some games. I don't think the majority of console gamers really thinks about it too much despite others saying it'll be a slideshow. (that is really an overstatement, unless we're talking Blighttown in Dark Souls on PS3.)
60 fps is more fluid and I'd personally like to see more action or fast-paced games targeting it in the future, but if they(developers) have to compromise by removing features/visual effects that may impact the cinematic quality or style they are aspiring to achieve in their game then I can see why they will go for 30 fps over 60. I don't really expect that they will ever come out and say that they "couldn't" get it to run at a stable 60 for that matter either.
Example:
Would you trust the guy selling you his game if you ask him if they got the latest addition to the super-awesome franchise "Batshit Crazy" in 1080p resolution and he replies "Nah, we couldn't do it. So it's 720p."
Even if he means well, and there's a lot of other perfectly logical development reasons that led to the decision -- that simple statement would simply echo in some people's heads as "lol, incompetence. gtfo."
I'm in a position where I can affect how people see my corporation based upon what I say internally and public. Let's say I told a customer that we "can't" or "couldn't" fulfill their most valued request of a million dollar project...then yeah..I'd have to go look for another job. It doesn't matter whether it's the truth or not -- if you got investors and a brand/reputation to look after, then you better make sure you mind what you say.
Bottomline/TL;DR:
I'm not claiming that ND might not make 60fps for Uncharted 4 because they "can't", but ultimately you have to remember that it is up to them. This debate or any similar future debates of other games will most likely do nothing to change the fact that the decision always rest with the developer/publisher.
I'm in the 60 fps crowd and will always prefer 60 over 30, but if a game I'm interested in runs in 30 and isn't on PC, then yeah, I'll still play it. If Uncharted 4 is 30 fps and you don't like it I recommend that you don't buy it, it's as simple as that.