However, links live on in a million places, and it's hard to motivate hobbyist webmasters of niche onion sites to migrate. On /r/Tor, we regularly get people asking why some onion site doesn't work, and it's a v2 site. That's two years after they stopped working. (I wish Tor Browser would detect a v2 attempt and give a nice explanation instead of an opaque error message, though)
The truth is that whatever schedule they could choose would cause allegations of it being too early.