That's something that will likely change pretty rapidly. Springboot 3 is forcing Java 17 which is going to force a lot of conversations once 2 is fully retired. (free support for 2 ends next year)

The Java 8->11 transition was rough but honestly after that we've not really experienced a whole lot of pain. 16 has been a little bit of a pain as well since it closed some more unsafe holes. I think that's the last release, however, that's going to cause major headaches with migrations.