Bitcoin tries to be two things:
A currency.
And a way to reliably account for who owns what, with no central authority.
As a currency, it has the problem that there's no natural demand for it. Nobody needs it to pay their taxes, and it's not widespread enough to be worth having for the common person. Naturally this could change, but until then you've got a game theory problem.
The protocol side is what makes it interesting. The protocol is basically a way for us to collectively scribble on a giant wall that grows every 10 minutes. And that wall cannot be changed, thanks to the clever incentive system that makes the primary use to account for who owns which bitcoins. The technology would still work if you used it to scribble love letters, but nobody would have an interest in keeping the system going.
So is this protocol useful? It very well could be. For instance, any number of currency-like things could be (and are) accounted for. You could put the whole land registry on the blockchain, and then you'd always be able to verify some person owned a parcel. You can put documents (or hashes of documents) in it and prove it existed at some time. The list goes on.
The big question is whether this protocol is economical and convenient enough to actually displace what's there already. We already have a land registry. We already have notaries.
There also needs to be some thought put in about how the infrastructure will be paid for. If the currency is useless, why do miners want to keep mining? Sure, there's the potential it won't be useless in the future, but how long can you string along an operation like that for? How do you plan if the price is so volatile it might be zero or a million in five years? Each price implies a very different level of investment.
One strategy might be a slightly different altcoin system (many, many altcoins have been invented) that tries to share the cost evenly, so no one economic actor has a special position. Another thing you could do is pass real money instead of BTCs.
But I think the protocol core is here to stay.