I'm not sure if this is a marketing move or they actually need more time for development.
It's bad for Nintendo to announce delays at the moment considering the months long drought there's been, it shows incompetence during a time Nintendo needs to prove itself.
On the other hand, they will have a big enough line-up during Christmas (specially in the platform department) for them to hold back Donkey Kong to keep the momentum going past the holidays. There are also no big exclusives for PS4 or XBone in December yet there is Infamous in February (the new DK release month).







