When everybody stops using OGL 1.0a. That's not a likely outcome, since there will always be small, amateur or not-for-profit publishers producing TTRPGs and related content. If they find something in an OGL 1.0a-licensed work they want to extend, they'll be doing that even if everybody bigger has moved on to the ORC or closed content.At what point is the fight over?
Hasbro/WOTC has a history of abandoning closed license plans for D&D after a few years (d20 System Trademark License, Game System License). OGL 2.0 is a closed license.