Thats if Titan was really aimed at compute performance (for an affordable price ), but i think they are more aimed with it now to a be at the top notch price. First, im pretty sure they will limit FP16, for dont push it in the feet of the Tesla, and when they are at it, im pretty sure they will disable FP64 too.
( if not fully, with a ratio ala 1/8-1/16 ) Difference could come from memory. as it have been allready the case, and full SP enabled.
So GP100-GP102, i dont know, i dont really see what could make so different a GP102 from a GP100, specially when we look at thoses Tesla PCIe.
Looking at the smaller one, i will not be surprised that the 1080TI will come with 12GB and the titan with 16GB.. ( or who know, maybe a 1070TI )