I don't think it was Sony but rather a choice from Naughty Dog. JaK 1 did very well. There was no reason to put pressure on Naughty Dog for edge driven sales. Uncharted 2 and 3 also did extremely well yet ND chose to go for a much darker and grittier game with The Last of Us. I'm sure Sony would have been all for an Uncharted 4 on PS3 instead taking additional risk with a much different and darker new IP from the same developer.
4 ≈ One