To me this seems fine. You'd run out of tokens pretty quick without ultimate anyway, so it is a small cross section of users this affects.
I am interested to learn if anything else is coming besides a billing change. Like will ultimate/assistant subscribers get access to MCP?
Well, no... I use maybe 1/5 to 1/3 of may month allowance on Assistant. It's nice to have. And I subscribed to Kagi also because of it. So, the Assistant going away would mean my expensive Duo subscription going away as well.