As you probably know (if you don't, read the Ubuntu 11.04 beta 1 post again), Ubuntu 11.04 will ship with an option to use the classic Gnome Desktop so Unity is not a must if you don't want to use it. All you have to do to use the Gnome panels is to select the Ubuntu Classic Desktop in the login screen.
Well, according to Mark Shuttleworth (see his comment here), there won't be such an option in Ubuntu 11.10 Oneiric Ocelot:
We made very good progress on a11y in Natty, but will miss the goal of perfect a11y. We'll nail it in Oneiric. That's OK, because we have the Classic desktop fallback in Natty, but will not in Oneiric.
Most probably (this is just an assumption) Unity 2D will be used as the fallback in Ubuntu 11.10.
I know this may not sound like good news to many but let me remind you that it will take another 6 months of development after Ubuntu 11.04 is released until Oneiric so even though Unity may seem a bit rough on the edges right now, it has a lot of time to improve.
Besides the obvious, it will also be interesting to see if Linux Mint and other Ubuntu-based Linux distributions that do not want to ship with Unity will still use Ubuntu as a base or switch. Or maybe they could start using Unity?