Due to irreconcilable differences in philosophy, our corporate German reseller and Bitsum has 'divorced'. This means the German translation must be recreated from scratch. Fortunately, we already have a new German partner working on this. Until then, we'll do the best we can to provide German users with the latest version, while at the same time not suddenly forcing a transition to English.
We apologize for this, but believe you'll be better off in the long run ;).
I've thought and thought about how to best handle this. There is no perfect solution. It will not stop the release of v5.1 though, even if the initial build has to be without German -- which appears inevitable at this time. I've temporarily suspended automated update notifications to Germany, Austria, and Switzerland at this time, for this reason. Hopefully the new translator will be able to complete the chore quickly.