Her career is over. She will have a prominent speaker position at the next convention but that's it. Should get together with Al Gore to campaign against the Electoral College.
As for 2020, I agree with Lisa on a couple of future candidates: Warren and Booker. Castro needs to get elected to something in the next two years. Resume is thin. I would also add Tim Kaine, Gary Peters (Senator from MI) and Amy Klobchar (Minn. Senator).
Outside shots - Gov. Inslee (WA) and newly elected CA Senator, Kamala Harris.