I hold open the idea that President Trump may decide (or even already has decided) to hold office only for one term. In that case, it’s only prudent for Pence and others to plan. Remember that President Trump is no spring chicken and may not want to suffer these DC swamp clowns for too long.
Trump is already doing campaign rallies and raising money. Every indication from him and the staff is that he is running in 2020. Trump is not a quitter and will fight the whole 8 years if he has to.
One day or eight years, he is still President and they will NEVER be able to reject or deny the FACT that DJT was POTUS #45!