There is also Kathy Radzuweit who will probably continue in Potsdam....but yes, German players either go abroad or retire quite early. You can't make a living as professional volleyball player for a very long time in German league, so the mediocre German players usually pursue different careers in their late 20s even if they could play some more years.
Some renewals: Rebecca Schäperklaus stays in Wiesbaden, Anna Pogany in Vilsbiburg.