I think this would be confusing.
Say.. the PostOffice stays stand alone in production for 2 weeks till someone accidentally drops a file with a clustered Queue. We would need to transform the PostOffice into a clustered one, from opening the JChannels to filling all the states. (Without also considering other implications on the data already existent on the DB).
But even if that was not an issue, it would require some development (mainly testing) on the PostOffice. IMO it would be better to use that energy towards 2.0.
+1 We're not doing any new features on the 1.x series unless there is very strong pressure from paying customers.
All new stuff is in JBM 2.0, 1.x is bug fixes only