I believe nossl was intended as a concession for schools that believe in censorship. It makes it relatively easy to configure things so Google doesn't go over SSL so that your existing MITM boxes which censor continue to function as before.

If they continue to support this use case, it may be hard to do without introducing bugs - one exposure to a 'real' service which spits out an HSTS header (or the preload list), and the machine loses the ability to conduct Google searches.

I think they'll either have to use some nasty workarounds, or they'll need to use a different domain - which isn't necessarily something you want to do when you are trying to provide simple rules which allow users to identify phishing.

More likely they'll simply force sites that want to continue to MITM to load their own CA roots.

Although I don't think this is their motivation, it also has the neat side-effect of making Google's Chromebook & device management services more useful.