No idea. It probably won't happen until 2037 at the earliest, maybe 2041.
2017-2025: Clinton
2025-2033: Clinton's VP, perhaps Castro
2033-2037 or 2041: Republican
2037 or 2041: white male Democrat
Do you actually think there will be Democratic rule for 24 years?
It is a far fetched scenario. But, if Ted Cruz is the GOP nominee, then Clinton will win in 2016 and possibly elected in 2020, over Tom Cotton. In 2024, Joe P Kennedy, if he succeeds Warren may do the same.
I'm gonna say if Clinton loses, Martin Heinrich is nominee in 2020, if she wins Joe P Kennedy is nominee in 2024.
George P Bush is undoubtedly the nxt nominee if Cruz loses, and will run in 2024.
A Bush vs. Kennedy election would be hell.