While Google could potentially abandon App Engine, it's much more likely it will simply remain unchanged for a number of years (as indeed it has roughly been for the past few years, save for Managed VMs).
GCP is now offering an increasingly larger percentage of what App Engine used to offer, so really the future may look a lot more like just build your apps on GCE + PubSub + Cloud Datastore and don't even mess with App Engine at all.
GCP is now offering an increasingly larger percentage of what App Engine used to offer, so really the future may look a lot more like just build your apps on GCE + PubSub + Cloud Datastore and don't even mess with App Engine at all.