AVM has released a new Lab firmware version for the Fritz!Box 7390 and 7340. The AVM developers seem to have worked really hard, a lot of work was done on the DECT, IPv6 and NAS part. The Lab firmware now supports secure DECT repeating mode, the AVM DECT phones will be able to display pictures included in RSS feeds and use custom PM3 ringtones. On the IPv6 stack RFC5969 aka 6rd was added, DS Lite is now supported.
You can find more details on the AVM Lab Portal. [UPDATE 2012-06-29 German version, the english version does not exist anymore]