Ret-cons add a change to a previously depicted scene or event. It changes the past. This doesn't change anything previously written and just adds to it. It's not retroactive continuity, it's just regular continuity.
Doesn't affect me. In no place in my campaign setting had I written that elves could not change sexes.
If someone wants to take that option, I have no strong feelings against it. It could be fun and lead to some interesting scenes and moments.
But I'm sure someone out there is super, super happy with this option and idea. So I'm happy for them.
This ^