Regarding the themes. Yes I think one "finally worked out" backend theme would be enough to ship with WB, other themes should be available for download as normal templates once the "technical things behind" are sorted out and guidelines are established for creating themes.
I think its important to have one working Theme which is easy to customize with a minimum of effort.
I also think that at the moment 3 shipped Themes pull to much attantion - attantion needed to make one really working an represenative Backend Theme.
I hope the devs (allthough this has more to do with marketing then with core) get this point, stop shipping three Themes and concentrate on one stable, working solution instead.
For this purpose there should /or could/ be started a own sub dev team, dedicated completely to the Usability and Workability of the Backend Theme (with some help core wise to figure out the core things needed to synchronise with the Themes).
Such a Sub Team would also be able to make guidelines (and recomendations) for use with Modules (Backend Templates for the modules).If you get me right, you'll soon see how important this could be for a appropriate Marketing of WB and its Modules.
One important part of Marketing has to do with making a good product visible and real.
We should concentrate on the reality of 2010 and stop shipping 2004 Themes with this wonderfull product.
Such a Board (sub team) was a dream of mine about a year ago.
And I still find that this is one of the most important (and most neglected) things in order to rise websitebakers Quality (and beyond).
This is something where the dev team shouldn't be involved to much into.
The Dev Team doesn't "sell" the product, has no need to do so.
Only if new Features needs to be integrated into the backend, they would work along with the Theme Board to get it implemented. It should be handled as a separated activity but with help in both directions.