Wouldn't releasing in the Spring get in the way of Pokken for Wii U? And potentially Pokemon Go?
Spring in games terms is most commonly May.
If it comes in February, then that's 3 months beforehand so not really.
GO is the issue, but they are separate things. If they have a Black2/White2 and Dream Radar sort of relationship, then it's possible to release around similar times, even though it'd make my life hell
The fact is, they wouldn't shift to this and reveal these 4 new Zygarde forms if they were over a year away, unless TPC has gone batshit crazy.