Java had major shifts in the language in 1.2 and 1.5. Java 8 isn't one of those cases. I think you'll find adoption won't be terribly slow.
Recompile away, stuff just works. Add lambdas to your code, compile. Still works. This isn't like 1.2 where you were adding collections classes (arguably for the first time) or 1.5 where you encounter generics.