If it's as long lasting as Doo says it is going to be (ignoring any 1st year production issues), there's not much advantage for a 4 stroke. Of course that's a big if.
Always be room in the market for both 4s & 2s and 850s have a long way to go ...many miles.... many years to prove to be as robust as 4s engines. I would luv to see it happen but highly doubful. We shall see/..... 2s have limits using turbos or go boom 4s do not. Composite chassis comes along and a lot of weight is gone...just saying tech moves quickly and OEMs need to have eggs in all the engine baskets. Look what the 4s Ace did in the low hp market ...who knew?... used to be all 2s air? lol