Bitcoin won't be the only p2p currency, just like Napster wasn't the only p2p filesharing software. There will be more, and they will improve upon the original. I have two suggestions for improvements upon the bitcoin concept.

1. More ways of mining the currency - Bitcoin awards currency as an incentive for contributing your processing time to running the bitcoin network. But why not have a whole suite of distributed computing aps that users can choose from? ie: like the SETI ap. Or an ap that rewards the amount of traffic that passes through your computer as a node on the Tor network? Or for running a distributed social network like Diaspora? The social nature of these distributed aps will further the propogation and adoption of the currency

There are all kinds of possibilities. Users would still have to contribute at least some of their CPU time & bandwidth to running the network, but they can combine it with running an ap that they find personally interesting, or one that they are using for themselves anyway.

2. Use Demmurage - I've been in love with this idea for a while (http://en.wikipedia.org/wiki/Demurrage_%28currency%29) Demurrage can speed up the circulation of the currency and prevent the hoarding that leads to inflation. It can be programmed to automatically adjust the demurrage rate in order to keep the currency at a predetermined value ie: relative to certain staple goods.