Open seat at the end of President Tom Cotton's 2nd term:
Juliana Salazar (NM-SEN)/Isaac Washington* (MS-GOV) 278 EV 49.4%
Vice President Elise Stefanik**/Bill Anderson*** (MN-SEN) 260 EV 49.1%
*1st black governor of Mississippi, elected in 2043 and reelected in 2047
**Formerly NY-GOV
***Formerly President, United Teleportation Workers of America
In short, Republicans make peace with unions and Democrats make peace with Mormons, parts of the energy industry, and most libertarians by 2030ish. MT and WY eventually go the way of Colorado.
The only way this could happen is if climate change models dramatically overestimated warning (they have over the past 2 decades, but it's unknown whether this trend will continue). I just don't see environmentalism going away on the Dem sides.