If I remember correctly, the Lumia 640 XL might get the "Fall Creators Update", which is essentially a huge massive amount of bug fixes, optimizations, and two features. But beyond that it's not guaranteed. You'll get security updates until three years after the phone has been released, ideally, but at this point Microsoft may only be releasing necessary security patches. The FCU is the last "okay we've done the best we can with this" before it's pushed to a very distant back burner. Set on low. And it's an electric stove. Running off a bunch of AA batteries. Inside of a freezer. Inside of a larger freezer. And the freezers are on fire.