I think its a great idea, and I bet they are re-evaluating they whole "ground up" approach after the map fiasco.
I think AAPL is smart enough to know when someone else does something better then them. To bring in huge and quickly growing customer base, especially since it has and continues to be a top selling app in their own store.
The hurdle for all this is 2 things I think, Ego and Android. Does Pandora want to risk that new Android customer? Growing fast and bigger then iphones, hmmm. I think if they feel they can make money with their model, which remains to be seen, then they would balk at a AAPL buyout.