ROKR hanging around the office right now to try this out, but Evan DiBiase may (or may not) have come across upon a rather important feature in iTunes: an upgrade for iTunes phones to remove the infamous, dreaded 100 song cap. We can definitely confirm that the above image / dialogue shows up in iTunes (snap taken from iTunes 18.104.22.168), but it's still not exactly the least oblique language in the world, we can only assume here. Still, we kinda figured this would be coming sooner or later -- if Apple wants any future in musicphones, removing that iTunes cap is absolutely completely necessary.
Update: Well, it was fun while it lasted. We've just received word from Apple that the 100-song cap is staying in place. Eddie Cue, the product manager for iTunes, spoke to Engadget's Ross Rubin, and confirmed that the upgrade screen exists for non-US customers, some of whom initially had caps as low as 25 songs, and brings their phones up to the 100-song limit. Of course, the very existence of the upgrade system raises tantalizing possibilities for the rest of us, but for now, that's all that's being raised.