Unless there's some announcements at E3 is P5 the only kind of big exclusive in the latter half of the year for Sony?
Big exclusive is very relative, since it could be argued Persona 5 is not among that category. There'll most likely be some surprise PS3/PS4 announcements for games releasing near the end of this year but, at this point, Persona 5 is among the few higher profile ones. If we consider only retail, it might be one of the only ones next to Hellblade, right now.
As I see it with my completely nonexistent localization knowledge, whether or not P5 is a 2015 game in the West has more to do with Atlus Japan than Atlus USA. I mean, if P5 comes out in the last week of December in Japan, there's not much chance we'll get it in NA this year. I'm not saying it will come out that late, obviously, but whatever the release date in Japan is could make all the difference.
That said, I have no doubt that Atlus USA is prioritizing P5, and to a lesser extent P4D. They wouldn't give us Lost Dimension if it meant negatively impacting their localization of the Persona games, so I'm sure it just fit their schedule well. And more Vita JRPGs is always a good thing.
The thing is, especially given how adamant they've been about the 2015 release date in NA, anything later than 2015 would simply be a delay. I'm pretty sure, at this point, they're already internally aware of when the game's set to release in Japan, and have been probably working on its localization for a bit now. The more projects they take on for 2015, obviously the more stretched their team would be among the different projects. As long as everything goes as expected, I suppose P5 should still be slated for a 2015 release here, but I'm not sure it would necessarily strictly be on Atlus Japan if it was pushed back to 2016.
Priority is the question, isn't it... We don't really know where their priorities lie, though we can assume Persona is pretty important for them to get out as soon as possible. I could maybe see a scenario where more localization projects to release this year becomes more of a priority for them than getting Persona 5 out in 2015 for the western audience.
Also: I kinda doubt Uncharted's delay will affect P5's advertising in any significant way. They may both be Playstation exclusives, but I don't think P5 will be the recipient of any unused Uncharted promotion budget.
That's most likely not happening, but now that the biggest PS4 exclusive of the year has been pushed back, that will naturally make it so more attention is brought onto the others, of which Persona 5 is included.