.... I'll disagree with all the assertions that a future iPhone would necessarily be a follow-on from the iPod.
I'll have a guess that Apple might surprise everyone and NOT include music-playing functionality in the device. It'll be a basic phone with an ultra-cool iPod-inspired aesthetic.... but no iTunes. Why not go for the divergence angle, and sell people multiple devices with a common design theme?
I mean, designer brands don't usually feel the need to bundle multiple products into one.... "yeah, I'd like the converged Gucci ShirtWatch please, and the Paul Smith TrouserShades"
... plus it gets around all the possible problems with mobile operators worrying about cannibalisation of their music revenue streams....