I confidently think that out of any potential newcomer, they are the most likely. I wouldn't quite go as far to say a lock, because who knows with the MH teams reluctance to add them to MvC3 and the lack of any hints in the Capcom data leaks, along with general unpredictability of Sakurai at times, but Capcom has a strong working relationship with Nintendo, MH has been relevant for Nintendo systems for a long time, and will continue to be so for the immediate future, it's one of the biggest Capcom series both in Japan and the west, and the Hunter probably has like 5 movesets worth of material to work with easily.