I think the main reason for a lack of first party support is from issues from internal studios
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I mean, we all know what happened to Stig's new IP from Santa Monica (RIP X() and how Sony Bend had three pitches scrapped for the Vita; for all we know, this type of issue happened to Sony's other studios in an attempt to get games running on PS4 :l.
I think what Sony's plans are this:
-E3 they announced God of War IV, Uncharted Collection and GG's New IP. Only Uncharted comes this year, with GOW coming in summer 2016 and GG's New IP being the big fall 2016 game.
-Uncharted 4 releases after GOWIV
-Ratchet releases alongside the upcoming film (early 2016)
-Sony Bend, Media Molicure and another studio announce their new IP's in Gamescom; all of them releasing 2016
-More PS3/Vita ports coming this fall; Beyond Two Souls and Heavy Rain come in a bundle this fall for PS4, Ratchet Future Trilogy comes this fall as well, Puppetter comes early 2016 to PS4
-Evolution continues to support DriveClub; hints at future Motorstorm game at E3
-Ready at Dawn and From Software continue to work with Sony; the former makes Order 2 for 2017 while the latter makes DLC expansions throughout this year and next year.
Just a few guess at what Sony might do; I feel that a number of their internal studios are gearing up for 2016/2017, explaining why this release line up for 2015 feels sparse. Lets up my guesses are right and that we get some great announcements this year for PS4
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