I haven't heard any thing official or even unofficial.
Splunk 5 was release on Oct 30, 2012.
If this is the answer you were looking for, please mark as accepted. Thanks.
The only thing I've been told by the after-sales team is that it's due for release in Q4, but I wondered if anyone knew an exact date..
The beta program is in progress (and has been for several months), but there will be no official release date announced (that is more specific than what you have already heard, Q4 of 2012) until it is actually released.