I assume the Reps are waiting untill the Dems are politically damaged by their obstruction- then call for a cloture vote when there aren't enough Dems present to block it.
The Dems would consider a "midnight vote" a partial victory [unless there is politicial damage from their obstruction]- better even than a recess appointment IMHO.
Actually, this won't work. The Dems don't have to have 41 seantors present to vote against cloture, the Repubs have to have 60 senators present to vote for cloture. If the Republicans can't get 60 votes, all the Dems have to do is keep one person on the floor to object to any unanimous consent request to limit debate. The rest can go home and get some sleep.