How do we ever know he's going to retire in 2028? He's still fairly young and Republicans always seem to go back on term limit pledges.
If he were to vacate his seat sometime in the next ten years, I can see Thomas Massie being his hand-picked successor. i could also see Andy Barr and James Comer give it a go, and quite possibly former UN Ambassador Kelly Craft. Perhaps Hal Rogers' eventual successor would also be interested.
I do believe Daniel Cameron is in line for the McConnell seat though, and I can't see many other Republicans vying to take him on. So the Paul seat will probably be the big competitive. The other row officers I think are mote likely to run for governor.
I think three terms is it for him....