No there isnt. Dolphin 7 is the upgrade to the current version.
After Dolphin 7 is a whole new platform I think it was called Posiedn, which they have already started working on.
Everything is explained in the boonex blog the first announcment on version 7
Here is a copy and paste of the one I am talking about
We planned for Dolphin 6.2, but while working on it we realized that
we have to change so many things and the whole script needs quite a few
structural improvements.
So, we've gathered all our programmers, including those working on
Poseidon, and fired up a one month program for the development of this
major update to the current Dolphin. This is going to be the last major
update before Poseidon, and we will only have smaller subsequent
updates (7.1, 7.2). In fact, Dolphin 7 is an attempt to create
something very close to Dolphin 8 in a nutshell, while the core will be
the only thing changing with the introduction of Poseidon.
As I said before - 7 is the bridge version, but make no mistake -
it's definitely not a fast-baked or temporary update. Dolphin 7 is the
result of more thought, more manpower and more planning than any of our
previous releases. Moreover, its mission is to introduce some strategic
shifts in technology, licensing and pricing strategies of BoonEx.