Some Chinese miners have already started talking about S17 being released next month, these guys are usually pretty accurate at least with the release date, they also dropped S9 price with psu from 395$ to 271$ for April delivery.

I am almost certain that next month will be the release of these monsters.

The S17 is expected to do 42TH at 1500w
S17 pro is expected to do  48TH at 1550w

The numbers on S17 seem very reasonable, in fact even 44th at 1500w is doable, not sure about the pro,it's a bit too much IMO. but let's see how it goes, will keep you updated if i get any confirmed information.