Hi,
You are correct in that Fusion 6 will not get official El Capitan support, but it might still work.
I would however expect Fusion 7 to fully support El Capitan, as for timelines.
This document Frequently Asked Questions about VMware Fusion has a list of when Fusion was released in the past.
It certainly isn't a guarantee for the future, but it might give you the general idea.
VMware itself has a policy to not disclose information about future releases and features, so in that regards there is no answer for the moment.
Hope this helps,
--
Wil