But for those who sync their iPhone and iPad content (apps, contacts, calendars, etc.) through iTunes... are they going to be told to sync their iPhone to "Music"?
The iTunes application on OSX is a very beefy app that does A LOT of things. For better or worse, stuff just kept getting added over the years.
Revamp "iSync", it's there, has been well before the iPhone as a conduit for syncing Contacts, Calendars, etc. in OS X with non-Apple devices.
A lot of us at Apple agree, iTunes should be "stripped down" to music. iBooks has its own bookstore, iMovie could handle Movie and Television purchases, the OS X App Store could bridge with iOS App's, allowing iSync to handle syncing.
For those of us using iTunes 12 beta, notice how this is halfway achieved? Each store is now accessed by the category you are in, that is you cannot access the Movie Store if you're in the Music section in iTunes.
The only issue would be non-OS X systems, and that is why Apple has not changed iTunes. Engineers would have to create MS counterparts for iMovie, iBooks, App's, etc. unless they leave iTunes for Windows untouched (which they could).