Dive machines do look great visually, but they're personally my least favorite B&M style. Once you do the initial drop, the rest of the ride tends to be a yawn. That said, they are generally a hit with the GP.
But as Freak said, I don't really know why SFMM would put in a dive machine with Hangtime just opening so recently. I guess they could make a "bigger, taller" version... but I'd really hope for something else for their 50th (if this is in fact what it's for). The elusive Giga would be the Holy Grail here, as would an extended single-rail coaster.
But yeah, having WCR for next year does throw a wrench in the planning. I think SFMM may have put themselves in a bit of a spot here... as known as the "roller coaster capital of the world", a lot of people (I would imagine even GP) would be pretty pissed off (or at the very least, confused) if they didn't put in coaster for their 50th. At the same time, if the coaster isn't impressive, or there's not coaster at all, just as many people will find it a pretty weak offering.
I've always felt what the park is missing, coaster-wise, is a wild mouse. Or an El Loco. But I'd have to admit, a wild mouse would be a pretty weak 50th anniversary coaster announcement. An El Loco could work, if they got one of the insane models first demonstrated. But I don't really see that happening, either.