Anythingbutipod.com published a Sansa Fuze disassembly today and allow me to offer a visual comparison of the SanDisk-branded main chips in the Sansa Fuze (top) compared to the one in the Sansa e280 v2 (bottom):
And since we know the e200v2 one is an AS3525, there is little doubt that the Fuze one is as well. Of course we can confirm this for real once we get our hands on a firmware update file for the Fuze – I’m not aware of the existence of any yet at least.
So where does this put the Fuze Rockbox-wise? About at the same position all the other “Sansa v2 architecture” targets: we basically know the firmware file format, we have data sheet for the AS3525 but there aren’t any particular efforts going on and we don’t know if they have any means to recover from being flashed with a broken firmware!
Update: because some less intelligent people decided that facts I wrote in this article back in 2008 would still be the truth several years later, I urge you all you check the date for things your read on the internets. And in this particular case, Rockbox runs very good these days on several SanDisk players that use the AMS chipsets. See the http://www.rockbox.org/wiki/SansaAMS page for details