If your map is already not compatible with 1.26, and you don't want to hassle getting old ver or making map compatible with old ver, you'd have to recompile/resave it with new world editor.
My prediction is that there would only be two standards, 1.26 (which is compatible with the third party nonsense), and whatever Blizzard shoves down our throats (just like they did with 1.31).
