In law, there are no extraneous factors deciding cases.
The point is, all cases are fact dependent, and a seeming slam-dunk can turn on the tiniest details.
There is a possibility for precedent, or the idea that the trademark itself covers such a wide variety of ground that it is in and of itself unacceptable (I doubt this will occur). The other possibility is that the two locations cover very different concepts under a generic name... Personally I think that Bethesda would have a much better shot at keeping their specific 'in setting' name than having to deal with the pretty substantial amount of WotC usage of the term.
Of course IANAL, just interested in copyright, trademarks, etc.
Slainte,
-Loonook.