The most important contract, the JVM spec, is really good in Java, and that makes up for almost everything. Javalang and the standard library is generally very good about maintaining backward compatibility (almost to a fault, some would say). Of course, there is code in the wild that depends on, for example, the com.sun packages and so on, and that extend the JVM using JNI - in those cases, all bets are off. But that was always true, and I'd argue that such contortions are generally as ill-advised as they are rare.

So, yeah, I think a faster release cadence is a good idea! Upgrading the runtime should be as simple as upgrading any other dependency.