I think it may be fair to say that the segments of 27.5 most likely to die are hard-tails and xc bikes.

I think it is also possible that 27.5 could die simply as a result of a self-fulfilling prophesy. All of the cries of "27.5 is dead!" may lead people to avoid them, fearing they will become obsolete and unsupported (like has happened to my high end 26er).