JEE spec conform archives should be deployable within the new server. Also EJB2 should work in a standard JBoss 5 or 6.
But the administration might be total different (e.g. JBossMQ -> JBossMessaging -> HornetMQ) and you have to read the documentation or compare the versions by your self.
If you have special questions feel free to ask in a community forum
thanks, we are currently running JBoss 5.1.0 GA. I am looking for solution how to upgrade it once when we will have to use higher version. I was hoping that in JBoss exist some kind of automatic procedure for upgrade.
In general the instructions in that link still apply, even for going from 5.1.0 to 6.0. And since the messaging software changed again (from JBoss Messaging in 5.1.0 to HornetMQ in 6.0), the general recommendations to redo any messaging configuration based on the new messaing server still applies, though of course the specific step are different.
As far as I know, noone has created an automatic upgrade utility.