[K-Thom]

After nearly two years the German market is still rather small.

You're quite right that the German book market is concentrated on ePub solely. But keeping its size in mind, this also is a rather irrelevant fact in terms of numbers. Amazon indeed is having troubles convincing German publishers (contract terms, price, format? I don't know), so they are having a hard time.
If/as soon as Amazon comes to terms with the publishers, the game will start all over again. Amazon just has to offer better conditions.

Most German publishers aren't in favor of eBooks in general anyway, so they will decide by the money they earn. The don't use ePub because they are convinced by it. They use it because it's the only available working solution at the moment.
Offer them an alternative - a better alternative in terms of infrastructure, and there the Kindle is by far superior to any European solution - and most publishers won't spend a second thought about ePub.

And I know but one German publisher who's advocating ePub because it's an open format. So don't bet on their loyalty to the format. But since we're a pragmatic kind of folks (if we want to), we may simply choose to offer both formats.