According to Bloomberg, Apple has approached a number of major music labels, asking for the ability to allow users repeat downloads of purchased music. This would essentially function as a backup of your purchased music on iTunes, so that in case of a hard drive failure or accidental deletion, you haven’t lost your entire music library.
It’s possible that, if successful, Apple would consider this part of their move to a system of cloud storage (allowing access to your entire iTunes-purchased music library from anywhere), and may be unveiled alongside a revamped MobileMe and an enhancement of the Apple’s increasing integration into the cloud.
Apple does seem to have some stake with the music industry, considering their massive consumer position, so I wouldn’t rule out the chance of them being granted their request – I certainly hope so – it’ll help me stop worrying about space so much on my iPhone and iPad!