I was wondering if someone finds a Glitch that MASSIVELLY improoves time, and that someone doesn't want to reveal how to do the glitch? Will the run just be disqualified or not accepted?

well, for right now there is no major glitches, or really any of the sort. If there ever is a glitch that is found that is major, there may be a subcategory for everything then, for glitchless and glitched runs.

Honestly, it's up to the community. If you found a glitch that, per se, skips a stage, but don't show how then we would probably assume its just a splice. If you have found a glitch, we would appreciate the info, but as long as you can show it's legitimate then it should be accepted. Unless it saves, as you put it, a MASSIVE amount of time, in which case it would probably warrant a new category.