Yes, yes, I know it is only a guess, but December 31st 2015 seems like a long time to wait! We don’t really know how long Naughty Dog have been working on Uncharted, of course. We do know that they have two teams; one of which recently released The Last of Us. I don’t believe their set up is quite as rigid as that suggests, though; several of the team that had previously worked on Uncharted 3; Drake’s Deception shifted to The Last of Us. I suspect it was an ‘all hands on deck scenario’. I would expect at least those people (and possibly some more) to shift their focus back to Uncharted for the PS4. And the idea of Naughty Dog having an ‘A’ and ‘B’ team is amusing. They just have talented people.
While I can’t tell you that the date given by Amazon is categorically wrong or right; this does seem like a good time to mention that Uncharted hasn’t been in full development for two years. I spoke informally with Evan Wells and Christophe Balestra after the BAFTA awards in London last year and they told me then that they still hadn’t made any decisions. This was a full five months after the release of Uncharted 3; Drake’s Deception. I wouldn’t expect them to tell me anything secret, but the manner of the conversation convinced me that they were not trying to cover anything up.
It is therefore my view that we will be waiting about a year, maybe slightly more, for the next installment of Uncharted. And I am prepared to eat my hat.