Someone on this thread a couple of weeks ago who appears to be in the know said that a new German route would be announced in "a few weeks", so we'll see what happens. I guess you'd need to announce pretty soon for a winter timetable start.
I would think FRA is tight for slots as well, but I think they are building a new runway there at the moment, so that should increase the possibilities for UK regional-FRA flights quite a bit. However, I don't think the new runway will be finished until this time next year?