There isn't much of a threat IMO as even the industrial-grade supercomputers won't even be able to crack a private key off of a bitcoin address. Also keep in mind that there aren't any commercially-available supercomputer anywhere that can come near the level of quantum computing, or even quantum computing in itself is still an exclusive privilege to experience. Again, it will potentially take hundreds of years before we crack SHA-256, before going in to the juicy tidbits of bitcoin's algorithm. Perhaps by then, humanity would cease to exist because of reasons..
If you look at the history of encryption, none has lasted as-long as it is assumed sha-256 will last. I think any encryption available today will be broken in 20-30 years. The reason I believe that is because the percentage of society involved with computing is extremely low, computers have been popular for what...25-30 years maybe? As that percentage increases, more and more minds become involved in the advances of computing, making the likely-hood of changes extreme. But, seeing as bitcoin is based off of the elliptic curve over Fp, it will not be a simple task.
But that's not how algorithms work, these aren't world war two codes, these are extremely highly sophisticated algorithms, more humans means nothing, they can't change the specifications o the algorithm.