Oh, I'd love to see Elizabeth Warren defeated, but it's hopeless.
This. Baker would probably be our best bet, but I suspect he'll go for reelection (which I would prefer.)
I doubt that Charlie Baker will run for Senate against Elizabeth Warren in 2018 as well, though he might run against Ed Markey in 2020 and could be competitive against him.
Baker has disowned the national GOP. It's really hard to imagine him going that route against the Dem current. Honestly his best next move is into a future Republican Cabinet.