They can always pass an law or amendment forcing future senates to always hold the hearing or always not hold the hearing in election years. Of course if next pres is a republican, expect the dems to be back in the house in 4 or so years (it usually works that way) and it may bite you in the ****.
Or they can enjoy the payback anyways when the time comes.
You are correct. I think it would simply be a Senate rule change that states a hearing must be held within a certain amount of time and a vote within a certain amount of time.
As it stands the Senate is under no obligation to even read the name of a Presidential nominee.