The Fuze and Clip + have very similar architecture. Judging on the song limit on the Fuze, I believe the Clip + will support up to 8000 songs.
Now with VERY general metrics, @ 128bit encoding a 2GB player can hold approx 500 songs. This equates to 4GB per 1000 songs.
Using this logic, the Clip + would hold 8000 songs which corresponds to approx 32GB total storage.
While this is mostly acceptable for the current 16GB SDHC cards out there (a maxed out Clip + would top out at approx 24GB). When the 32GB MicroSD cards hit the market, even a basic 2GB fuze with a 32GB card would max out the 8000 limit.
If you are encoding at 64Kbit, it is possible already to max out the limit.
The Fuze went from 4000 to 8000 with the latest firmware. It is hoped that when 32GB cards become a “reality” that they will increase the limit again. Again if you go by the general 500 song per 2GB @ 128bit forumula, A fully maxed out Clip+ / Fuze should have a minimum 10000 song limit to the database.