John McCain (2009-2013)
Mark Warner (2013-2021)
Sarah Palin or more likely someone not on the national scene (2021-?
)
Barack Obama (2009-2013)
Mitt Romney (2013-2017)
Mark Warner (2017-2025)
My gut tells me that the next POTUS will be a one-termer, whether it's McCain or Obama. If it's McCain, it'll be another close election in 2012 with Warner winning against either a very visibly aged McCain or against the VP since McCain has decided not to seek re-election. Warner is easily re-elected in 2016 and Palin wins a very close election in 2020.
If it's Obama, the GOP is energized behind Romney in 2012, who wins a close election but loses to Warner in 2016.