I think he's too tied to Texas in some ways, but he could run well as a veep for some other candidate unburdened by a pyrrhic loss. More importantly, his campaign's a strong example of 2010s U.S. grassroots politicking and voter engagement through registration. Those high numbers for youth turnout tell me something's working! I agree with others that Beto's rather wimpy, though he's got some nice liberal/left-of-center platform points that could go somewhere. And we got downballot victories here thanks to him; I'm really glad to see Collin Allred oust Pete Sessions for good reasons.
Still, it sucks that if he runs, Trump's going to rail on his loss for a million gorillion years. Must be nice to always win because you constantly destroy everything around you without dying yourself.