IIRC, the next JVM will indeed offer a new operation that allows tail calls (not exactly tailrec). However, this operation is incompatible with the Java security model (what you're allowed to do depends on what's above you in the stack -- this is used in many places in Java, in particular for anything related to accessing the screen or the file system, or more generally anything involving JNI) and with the Java exception model (exceptions contain the whole stack). Therefore, the operation will not be used by Java itself, and there are chances that using this operation in JVM languages without breaking compatibility with the Java stdlib will take some work, at least for the features that relate to security.
