A few thoughts...
I could be wrong, but I don't believe the vice president gets to vote (as a tie breaker) on parliamentary rule changes in the Senate.
So if the Pubbies hang tough, the DCP couldn't get 51 votes to change the rule, anyway.
Having said that, I asked this a day or two ago, and will ask again:
Is Dianne Feinstein currently showing up in the Senate?
I read that she literally dropped out of sight a couple of weeks ago due to health reasons.
I could be wrong.