It's too far out to say, and it's not even likely to be a current candidate running for the presidential nomination. Neither Tim Kaine nor Mike Pence were even considered long-shot candidates for their party's nom in 2016, and they were the VP nods. Likewise Biden polled far behind Edwards, Clinton, and even other long-shots like Kucinich and Richardson in 2008. Dick Cheney had been a career Republican white house strategist in 2000, but never had aspirations at running for president, likewise with Al Gore in 1992. It's uncommon for the VP nod to go to someone who is actively competing in a presidential primary. Biden in 2008 was a modern anomaly, but even Biden was well out of the race early on in the 2008 primary which had become a two-horse race quickly.
That said, who I'd *like* it to be entire depends on who the nominee is and it's tough to say until there's a nominee or clear front-runner.
I think if the Democratic nomination goes to a more centrist Democrat, and if we're picking from the current crop of aspiring nominees, then I'd *like* to see Warren get a nod to be VP. I think she'd be a really effective vice president because she's from the senate so she's aware of senate procedure (one of the roles of VP is to break ties in the senate), she's a good attack dog in debates, she has a strong policy background so she could campaign for the nominee in an effective way. I don't think she aspires to continue to be in the senate, and I suspect a rising crop of young Democrats will be aiming for her seat, particularly Joseph Kennedy should he not be successful challenging Ed Markey.
I also think Warren has the countenance to be a vice presidential nominee if her campaign for president ultimately falls short... As in, she's willing to defer to the establishment when party unity calls for it, which I don't think another progressive candidate like Sanders wouldn't do as easily.
If a candidate like Sanders is the nominee, then I don't know. I don't think he can nominate another New England progressive like Warren as his VP. And I don't know whether other moderate candidates in this race would want to be his VP. I think a politician like Stacey Abrams from Georgia could work for a Sanders' nomination because she brings diverse opinion, is from a geographically different area than Sanders, from a large metropolitan area, has legal experience and has run for executive office (unsuccessfully, but ran an excellent campaign). Buttigieg would also benefit from Abrams as well, I think, though Abrams is mode moderate than Sanders on policy, closer to center-left, so it's a better fit for a progressive white male candidate like Sanders than moderate-left white male candidate like Buttigieg.
I also think Tom Vilsack is a potential front-runner should a candidate like Biden or even Warren get the nomination.
But again, it's a long way off, and VP noms are usually not even prominent candidates in the primary, so who knows.
Candidates like Yang would never, ever be a vice presidential nominee. Yang does nothing politically for any candidate, and he'd be a distraction for every candidate because he's hinging his presidential run on being an outsider with out-of-the-norm political ideas. You might like him as your nominee choice, and that's fine, but if a front runner goes with Yang, then they're going to be constantly pinned down on his very niche political proposals and have to answer for them, even though they're not the nominee's policy proposals. If a Warren or Sanders wins the nomination, they don't want to answer questions about Yang's unorthodox policy proposals (namely, UBI, something that even the most progressive candidates in the Democratic party don't endorse as policy even if they might agree with the basic argument for it). For progressive candidates like Warren or Sanders, 'The Yang Gang' is likely already going to vote for a Warren or SAnders in the general election; for more center-left candidates like Biden, Buttigieg, or others, Yang is political baggage that would cause them to lose some center-left support while Yang's supporters would still not fully endorse a moderate left nominee, or at least, the "minus" would exceed the "plus." Yang also does nothing to build a base, he's a "coastal elite" technocrat, and in a race where the Right is going to certainly paint any Democratic nominee as part of "The coastal elite out of touch with real Americans," you basically can't find a better example of that than Andrew Yang.
I think if Harris and Warren don't get the nomination (well, obviously not Harris...) or a VP nod, then both would be appointed to cabinet positions in the next Democratic administration should whoever the nominee is beat Trump. THey're both senators from safe Democratic states. Harris in particular is in line for a DOJ nod, given her background as Attorney General of California and District Attorney in San Fran. Incidentally, being a senator from california makes her a very safe administration pick because she'll almost certainly be replaced by a Democratic governor and then California will elect another Democratic senator to fill the seat. Warren, similarly, though I could see her as head of a newly reinvigorated Consumer FInancial Protection Bureau, and her seat would definitely go to another Democrat.
Julian Castro would be another strong choice for most candidates, too.
