I'm in the same boat. I think I'm likely going to stand up a Nextcloud instance on a VPS for calendar/contacts/docs and move mail (somewhere). Paying by user/mailbox is really not a good deal for the way we've been using it, so it will either be someone that charges based on domain/traffic/maibox size or something self hosted for received mail with a pay-per-message smtp smarthost.

It's really not something I'm happy about needing to figure out all of a sudden.

This +100. I'd pay a reasonable amount for my Google Voice numbers, too, if it would ensure that I don't lose them on short notice.

Same.

I am OK with paying $6/user/month for the new plans but they don't include Google Voice, which is $10/user/month. I would be ecstatic if they had a cheaper plan that included Google Voice or if they allowed me to migrate my Google Voice number/account to a regular Google account.

Can you port it out and back in?

It's possible for now but you lose all your history, settings, etc. And my Google Voice number has been primary number for a decade or so and thus has a lot of important stuff that I would like to keep.

I was able to migrate a Google Voice number and history from one @gmail.com to another @gmail.com - IIRC there was someone on Google support forums who I messaged with and after validating accounts they put it in some queue or something. IIRC a day or two later it was all there. Magic.

Hasn't there always been a 10 user limit? That's what I remember at least.

Up to 100 users was a thing

Many more. I opened (and still have) a 500-user legacy account, and also have two 200-user accounts in case anyone is interested.