Haven't all SE games with the exception of the FFXIII series been exclusive to one system or the other? I don't think it'd be wrong for anyone to assume prior to the announcement that KH3 and FFXV would be Sony exclusives. Especially after their announcements coming during the Sony show.
While there was clear favoritism, and notes of what initial development was made for, that doesn't necessarily mean a publisher will rule out the opportunity to widen the pipeline of sales. However, in general games like Kingdom Hearts, Final Fantasy, etc. have been more or less synonymical to Sony owned platforms. Yet at the same time we saw so many platform jumpings with the handhelds for various KH based spin offs.
It's a little too soon to say anything yet, but it certainly wouldn't surprise me if this generation of game releases became reminiscent of the (good) ol' days of exclusivity wars.