bundle v.0.7 vs newer bzr.dev: no backward compatibility?

[Alexander Belchenko]

I try to merge old bundle with newer bzr.dev and get error hat say about 
bundle v.0.7 is not supported. If I understand correctly bundle 
mechanism is not mature yet so backward compatibility is not provided? 
It's not problem for me. Just want to understand: in future there will 
be only one version of official bundle format, right? And now version of 
bundle is only for bundle reader?

--
Alexander