the way the senate goes so goes the supreme court
Actually its "the way the Presidency goes so goes the Supreme Court."
The President gets to appoint the Supreme Court judges. If Trump is elected he'll get to appoint judges that he selects. The Senate may try to hold up the process, but sooner or later they'll have to approve someone he nominates. To do otherwise would set a precedent for the future that even the most stalwart liberals would not want to have.
Having a majority of real Republicans in the Senate would be great, but the current crew hasn't shown themselves to be reliable, or really able to do much of anything.
I repeat there will be a replacement Supreme Court Justice before the next President is sworn in.