Re: "we have signaled a last time to buy"
"Last time to buy" is for customers who already depend on the product. It's a standard mechanism to provide business continuity.
Say you design an AR escape room and use HoloLens as your platform. Microsoft will contact you and say "yo, we are discontinuing these headsets, so tells us how many you want by such and such date". Then you figure out how long it will take you to move to something supported, estimate how many headsets you will need before then, and order them.
At a previous workplace, whenever we discontinued a product that supported $COMMUNICATION_STANDARD we would get substantial orders from existing customers. We were the only company support for $COMMUNICATION_STANDARD, and the people still using it wanted to get as much time out of their existing installations as possible. Ordering a few dozen of our parts at that time for use as spares made sense for them.