Wow--I'll wait until I hear of someone seeing a 2018 at a dealer before I completely believe it, but if it is true, how much web churn was spent on this!?
Yamaha's site has a 2018 model page: here. And the search inventory page says "Dealer delivery for this model begins September 2017", and here's a CycleTrader ad for one at a dealer in Missouri but their official website doesn't have it (a common lead gen technique).
I have to say, I was thinking it was cool after buying my 2017 to think I got in on the last year. If this is in fact true I'm happy for those who will be joining the club.