It was supposed to be released with Java 7, but the status is Dormant. On the other hand, the same page says
Use generics in the JMX API, for example have
I asked this question also to the current product manager for JMX at Oracle, Tuva Palm some times ago (September 2011), and she promised me, that JMX 2.0 is not dead and there will be a technical roadmap in Q1/2012.
However, nothing have happened until now and even worse, JSR-255, the JMX 2.0 spec (but also JSR-262, ther WebService connector stuff) has been marked as withdrawn since 2016 with the following reason:
JSR 255 specified changes to javax.management.* which were subsequently abandoned due to lack of resources, and were not included in the Java SE 6 or 7 Platforms. (The changes were distinct from other changes to javax.management.* specified by JSRs 3, 160, and 336 for inclusion in the Java SE 6 and 7 Platforms.) It was determined in 2014 that future changes to JMX technology would be specified directly by the umbrella JSR for the Java SE Platform.
So JMX 2.0 in its original form is factually dead.
Apparently, it was postponed to JDK 8, and all already made changes reverted, so JDK 7 final implementation should be the same as JDK 6.