I didn't want to open a new thread for this, since so far it is just mere speculation. According to an article from
Teltarif (in German) there will be a new auction for the remaining UMTS (W-CDMA) frequencies next year.
Possibly Germany could finally get it's fifth mobile network, the article suggest 3 (Hutchison) and AT&T.
Active Prepaid SIMs: United Mobile; (RC)
China Mobile; (USA)
TúYo; (D) Loop, Callya, Simyo; (A) Klax; (I) Wind; (B) Ay Yildiz
Former Prepaid SIMs: (RC) IF; (D) Free&Easy, Xtra; (A) Yesss; (UK) Pay&Go; (E) Movistar; (IS) Frelsi
Mobiles in use: Sagem my101X, Siemens M50,
Nokia 6800,
Siemens M65, Motorola E770, Samsung SGH-Z500, Nokia 9500
Previous Mobiles: Nokia 5130, Motorola V3688, Sagem myX-1, Siemens M55, NEC e313, SonyEricsson T200, Motorola V980, Siemens C45, Motorola V600