46. Kamala Harris (2021-2025)
47. Nikki Haley (2025-2033)
48. Dan Crenshaw (2033-2037)
49. Unknown Democrat (2037-2041)
50. Unknown Republican (2041-2045)
Taking another stab at this:
46. Joe Biden/Kamala Harris (2021-2025)
47. Nikki Haley/Josh Hawley (2025-2033) (def. Harris/Buttigieg and Buttigieg/Ocasio-Cortez)
48. Mark Kelly/Stacey Abrams (2033-2037) (def. Hawley/Unknown Hispanic Republican)
49. Young Hispanic Republican/Older Party Statesman (2037-2045)
50. Someone like AOC but probably not AOC herself/Older Party Statesman (2045-2053)