The only het end I can guess at, would be Keiko getting back with her ex and restart from there, with Ran supporting them, while trying to get over her crush. That woud send people waiting for yuri in a fit of rage (including me) but that wouldn't be an bad ending if Keiko can find happiness. As for Ran, well, heartbreaks happen.
Anyway, the way the story goes right now, unless something big happens to get them closer than they are now (which is already a lot), I can't see them getting out of the friendzone.