Doesn't have to be 6-9 months thanks to the competition. AMD aren't expected to release new gaming GPUs until 2020 now. Navi = PS5 in 2020; no gaming Vega on 7nm ever.
Do not believe this. PS5 may use Navi IP but that doesn't mean the desktop and mobile models will be released alongside.
Navi is one year away, in the worst case.