So at least a license update would require confirmation of your continuing agreement with the new license, right? (whether that be silent, offering opt-out or whatever).

Otherwise "you agree to ANY future version" would equate to "we can 100% rewrite this agreement after you signed it". Doesn't seem like that would hold up in a courtroom.

Game engines ship with products & are covered by licenses. Unlike some service covered by a ToS where company can change or stop offering service at any time.