High sales made Sony delay another PS4 price cut for a lot of time, but with sales finally starting dropping more significantly than last year, a price cut will most probably happen, next September could be the right time, and in that case MS should follow to keep XBOne alive.
But even delaying the cut longer, next year it will be absolutely necessary, so when 9th gen launches, at least base 8th gen models will have a substantially lower price than 9th gen, even base ones. Old gen will target a different potential user base and it will make sense to keep it on the market for a couple of years.
Obviously old gen production will gradually drop, and when 8th gen SW sales will have dropped a lot, then HW production will finally stop.
Except for consoles that were utter failures and were immediately killled, it's the same thing that always happened to old gen at every new gen launch.