Who said the keys need to be long lived in WKD? WKD just makes the key discovery easier based on email address, you can rotate your key as often as you want (just set the expiry date so clients check it).
Also, I'm not sure if I get the "public ledger" part as WKD I just your own HTTPS server. It doesn't have anything in common with keyservers.
This is not the only example. I never ceases to amaze me that Google dropped XMPP because of non-mobile-friendliness and it was proven wrong by a single developer (see: Conversations.im).
It seems in a lot of cases Google just want to go on an easy route of creating fake "standards" (AMP) instead of long way of working with broader community for common good.
Maybe that's just me but the Google I remember back when Android was announced and the company it has become now it's like two totally different entities.
> The people who had been using it would continue uninterrupted.
I'm not sure about that. If the main matrix server disappeared today that'd be problematic. Yes, you'd have history locally but the same can be said for any native client that stores history locally.
As far as I know there is no way to migrate matrix history now. Is there? (genuinely curious)