In theory, yes. In practice, if you own a currently 4+ million dollar home built in the 50's, you are paying at least 15-20k on it anyway.

Here's an example currently for sale:https://www.redfin.com/CA/Los-Altos-Hills/27446-Black-Mounta...

They are paying 18.2k.

If it was reassessed today, they'd be paying 40-45k.

If they do what most people who have lived in a home forever do, and are downsizing to something smaller (IE kids grew up, whatever), they will likely end up with either the same or less in taxes they pay now.

So it's not like right now they pay nothing, and they'd pay a ton, it's "they pay a lot, they'd pay more".