My guess is that now there are a lot of people/teams, as ingenious and educated or more so than "Satoshi", who are working on even better p2p currency.
Don't underestimate the power of the Bitcoin protocol! The currently enabled functionality in the client is but a small fraction of what's possible. Instant transactions, real micro-payments, true anonymity, free automatic escrow, scalable blockchain and much more is what's coming to Bitcoin in the next years. And no, these are not just items on a wish-list but all perfectly possible with the current Bitcoin protocol! It's just that none of the clients makes use of them because it is really hard to get the implementation done right without introducing possible security flaws.
Besides, even if another P2P cryptocurrency with superior features came along tomorrow - it would first have to prove itself over time to be at least as secure as Bitcoin has turned out to be over the last 3.5 years. People are not going to trust serious amounts of money to a system that hasn't been thoroughly scrutinized by a lot of experts for some years. We're not talking about some fancy P2P filesharing protocol after all.
Having said that, I still voted only "within a decade".