Apple may well follow in the footsteps of the likes of Napster, Real and Yahoo! if it offers a subscription based service. They might not be keen on the idea, but if that's what it takes to crush the competition, then that's what it takes, end of story. So they may well move to a subscription based model for their iTunes digital music online store in order to remain competitive.
Apple has reported that they could start offering a subscription-based model for downloading songs from the iTunes by the year's end if they notice any loss of revenues to these emerging services. This would be to protect the interests of the consumer who have bought iPod. Apple prohibits iPod to play songs downloaded from other online stores. This is a primary reason why they manage to sell a million plus songs from their iTunes music store on a daily basis. iPod is a Hot Seller in the market.