Given the dangers of the XID wraparound, I wonder if it makes sense for Postgres to auto-launch a Vacuum Freeze, or some minimal variant of it, when it detects that a XID-wraparound is imminent.
But on the other hand, it starts warning you, first just in the log file, then on every query you issue way before it actually stops working, so if you're not ignoring warnings in your logs / your client-code, there should be ample time to react.
At least, there was for me when I first ran into this a few years ago.