An interesting discussion here. The good thing is that if necessary, the crypto algorithm used by Bitcoin can be updated without too much work. Provisions are already in place and this has been demonstrated by the Scrypt-based forks of Bitcoin, like Litecoin.

I can already hear the cries of "Quantum computers are ruining Bitcoin!" which will of course follow the current echoes of "ASICs are ruining Bitcoin!" which were preceded by the lamentation "GPUs are ruining Bitcoin!"