I don't know for sure, but I would say something non-SPS. Mainly due to the crazes tending to be the easier to keep species and appealing to a wider group of hobbyists. They also need to be easily fragged.
I know Blastos are starting to gain appeal as are the uniquely colorful Tracs we are seeing from Tonga and Aus. I don't think the latter will catch fire though as they are difficult to frag. Favia and Favaties perhaps.
I know I will be happy when the next trend kicks in though. As those whom I have purchased or traded with can attest to, I don't mind dropping some $$ for something I like that is healthy. But seeing an Acan colony cut up into single polyp frags is a shame.