Even if a second password is required, I still feel that we should update. It'll decrease the security risk that way (the less the security risk, the better), and we need to get the structure data saved for the eventual update to 1.7 anyways (you like having wither skeletons and blazes naturally spawning in nether fortresses, right? Well if we don't get the structure data saved, they won't spawn. Same applies to witch huts.)
I tried going to other servers in 1.6.4 and something was up, I say wait till 1.7
Can you clarify on what this "something" is? "something" is a fairly vague and unhelpful term.
Also, again, we do need the get our structures saved. We can't just wait for 1.7 and lose out nether fortresses and witch huts. Finding new chunks is already going to be a pain for explorers that wish to see new terrain. Don't make it affect those that farm wither skeleton drops naturally too.