Can we upgrade the network from SHA256 if we needed to?

If SHA256 goes the way of the dodo like MD5, on what scale from trivial to impossible is it to have the hashing algorithm for mining and private keys etc to be upgraded to something like SHA-3?Is it a matter of getting everyone on board, or just a majority of developers?Would this be closer to a soft fork or a hard fork?Is SHA256 so different to MD5 that this not at all likely, or is it an inevitability within our lifetimes that we eventually need to think about and plan for before it's too late? via /r/Bitcoin http://bit.ly/3a9vOLv