Is searching really so hard? There are dozens of threads discussing this.
The answser is: yes, it is really hard searching something in these vBulletin, SMF, etc boards. But I've tried without success. That's why I kindly asked for links.
First, let me say that there is no vote. A change to the hashing system is automatically a hard fork. If SHA weakens enough to concern us, the support for a transition will be overwhelming, so approximately everyone will follow.
The "vote" is the confirms of the solved block. If the majority of power confirms its own blocks, the chain will fork.
If I'd have a huge farm of ASIC miners, I'd give away any hardfork that put my inversion into ruin.
Second, modern cryptosystems don't typically have sudden catastrophic breaks, they get weaker over time. Bitcoin's design gives us even more safety margin. MD5 is considered to be hopelessly broken, and should not be used And yet, if mining was based on it, we'd still be fine because all of the preimage attacks require more freedom of input than bitcoin allows.
I didn't mention sudden catastrophic blowups of the algorithm. Any analysis that shows slight departure from the Random Oracle model, in such a way that given the freedom of input, it is possible to construct hashes lower than target with tiny higher probability than random, is enough IMHO to move away from SHA256d.
Third, an orderly transition away from SHA is certainly possible, even in the ASIC world. In other threads on this topic, I've described one possible way to make the transition, but there are certainly others. It would take time to happen, but, as described above, we'd have plenty of it.
I'd love to read these threads. I'll search more intensively...