The technology behind it is secure - for the current time. If quantum computers are developed then we might be looking at a different story. The thing with technology, though, is it evolves. If something were to happen to show that Btc was exploitable, there would be a fork or a replacement that wasn't vulnerable to that hack.

Currently, I'm not too concerned about it - I think we're a long ways from having the type of computer necessary to do this sort of thing.