PS4 is going through the awkward phase of Japanese devs not wanting to make games for it because there's no real userbase, and Japanese people not wanting to buy it because there's no Japanese games.
IMO, the success of GTAV ( and to a lesser extent, the rising popularity of games like CoD, etc) in Japan is paramount to any hope of PS4 gaining some measure of success there.
I've said this before, but the faster current-gen sells globally, the faster western developers will skip last-gen hardware, and that would make available more western 'current-gen exclusives' for Japan.
Sure, ultimately, they're western games that won't move the needle too much, but a multitude of all those games, especially taking into account their increasing popularity should, in the short-term build enough of an install base to compel an earlier jump of hardware sooner rather than later.
That, and Sony better pray hard for FFXV to come out Holiday 2015 in Japan. I've already got my hopes for current-gen only MGSV TPP dashed when the latest trailer confirms it's still coming to last-gen. That was a game that could've moved hardware in Japan if it was current-gen only.