AFAIK, Hadoop is converging on Avro -- not sure about the state of each component within Hadoop with respect to avro, but in long term, I expect it will be the protocol.
Hadoop is NOT converging on avro, there are significant political barriers, and at the very least Owen is dead set against it. The comments on the latest JIRAs are rather pessimistic.
Patches have been rolled back, commits vetoed, and the direction seems to be providing a pluggable thrift/protobuf/? RPC option, which seems weird to me. In any case, there was a lot of back pressure to avro.
Also given it's complexity I dont think I can recommend it in the RPC area.
