They would indeed be very stupid to do this. Even if the plan is to get rid of exclusives, they can’t possibly be in this big a hurry. There are several other titles that aren’t considered flagship that they can ship to other platforms first, before looking at Gears, Halo, Forza. On the other hand, Phil Spencer did say they hope people will start to love Xbox after having played some of these games. It was something along those lines.
So, what if they were to release the collection of older games, but no word about other platforms when they announce Gears of War 6? Hoping people might consider subbing to GP and/or getting an Xbox? It’s not impossible. That being said, it’s not what I’d consider taking it easy and baby steps. But at some point more games will move over.