Shardstone
Hero
Hopefully never. Keep 5E evergreen and only do small updates on it. If D&D is to be super mainstream, you can't reinvent it all the time.
I won’t be surprised if revolution or climate collapse happen before 6e, and the chances of there ever being a 6e decrease dramatically after either.
50th Anniversary will see something big, but it won’t be a 6e by any reasonable standard.
It will probably be less different than Essentials was from PHB 4e, and the two were completely compatible.
More like a special edition reprint with slightly more aggressive errata. Possibly a rebuild of some unsatisfying options, but probably nothing even as dramatic as any given designer wants to do.
DnD is Adv/Disadv, Bonus Actions, Bounded Accuracy, and Hit Dice, now. Full stop. WoTC’s goal has always been and will always be an edition of dnd that that becomes a household name that you can come back to twenty years later and it’s pretty much the same as when you left it, but with more options if you buy the expansions.
I doubt you will be happy with whatever 6E turns out to be.Not soon enough, that's for certain. I was ready for 6E in 2017.