If Clinton is a two-term president, who is on the Democratic bench in 2024?

[Mr. Morden]

Elizabeth Warren, Tammy Baldwin (assuming she survives 2018), Kirsten Gillibrand probably.

Elizabeth Warren will be 75 years old.  Doubful she'll be running at that age.

I do think both Gillibrand and Klobuchar would stand a good chance of running, as they both seemed to want to run this time around, but couldn't because of Clinton.

I don't know though.  I'm guessing the majority of candidates will be people who don't yet hold statewide office, as of now in 2015.  Though whoever the vice president is will presumably be someone who we already know right now, and I'd assume they'll probably run for president in 2024.

[Mr. Morden]

And of course Hillary's VP will be the presumptive nominee, so will the Dems even go to the bench?

Depends on who it is.  Is Tim Kaine exciting enough that he's going to clear the field?  I mean, in this scenario it will have been 16 years since there was a truly contested Democratic nomination fight (I'm not counting 2016 as being "contested", since Clinton alreay has it won), and surely there will be a number of potential candidates who are sick of biding their time and deferring to the frontrunner.