I always expected it to be on PS4 tbh. Was there a reason it wouldn't have been, like rumours of an exclusive deals or something to do with Kojima/Sony?
It's more to do with Kojima's previous track record and the fact he's renowned for being a bit of a perfectionist. Since, Kojima, doesn't need to build his own engine this time that has probably cut down the production length drastically. So hopefully that means I'll be able to play this before I turn 30.