You think they should wait until SHA-2 is broken to start looking for a replacement? Think about that for a second.
If they think for a replacement there is a reason, right? If they think for a replacement after 2012 why you shouldn't? Or you intend to use SHA-2 until 2140?
They need to make a replacement becqause the alternative is to wait until SHA256 isn't good enough.
Yes, bitcoin can change to not use SHA2