Since dotty/Scala 3 is going to swap the meaning of these two (already does with a flag -source:3.2), would it be possible to support it in kind-projector, to be able to cross-compile Scala 2 / dotty projects with new syntax directly, without going through intermediate * period.

That would be convenient for those projects that are more comfortable making 1 syntax jump right now, instead of 2 syntax jumps in the future.