Of open source evangelism, just like evangelism for the personal computer became unnecessary within a couple years of the release of MS Windows 3.0. Even CEOs (who previously said "I don't even know how to log in, I have people working for me who do that") and grandmothers got on board at that point.
Even Microsoft is busy trying to figure out how to use open source software as a strategy to attract developers and customers.
It still has to be promoted & nurtured and protected from being co-opted. Fail to do any of those and it won't be long before it's back to being a niche.
Perhaps when an opensource desktop OS reaches macOS usage levels in the advanced Western economies we can relax a bit.