Conventional tech wisdom tells us that convergence will conquer all. People don't want to lug around multiple devices when they can have one device that does it well. Sadly, this isn't as easy as it sounds.
Take, for example, two pieces of tech that seem pretty standard issue now a days: the cell phone and the iPod. Motorola tried to combine the two with the ROKR and it didn't work out all that well (they were even working with Apple). The trick is that you can't just combine a crappy phone and a crappy MP3 player and hope for the best. This is why the iPhone rumors are so persistent; Apple is known as a company that 'gets it' therefore, so goes the thinking, an über-phone from Apple will solve all of our problems.
The Nokia Music Manager which allows you to transfer songs from iTunes to your phone.
So, will customers clamor for all in ones and leave Apple behind? I can't predict the future, but at this point I wouldn't bet against Apple, though the N91 does look pretty slick.