[IriDium]

I would image that running the nightlys on RC1 would be the equivalent.

There is no planned release, as I expect RC1 needs to be bullet proof first, then work can commence on RC1.1 (Gotham).

As Gotham is just changes to XBMC and not core Xbian it's only really XBMC changes to say the DB and factors that could affect XBMC xbian-config (Of which there are a few) that need to be addressed.