No, I don’t see them voting down Brexit, any more than Republican Senators ever were going to endorse Hillary Clinton, even though many of them are rooting for her. The more likely scenario out of Brexit is simply that Parliament stalls, demanding that Theresa May give them “the right Brexit.” Of course there is no such thing, wrong Brexit is wrong Brexit, if only because EU-27 cannot agree on very much. But with enough stalling, eventually another national election will be held and of course Brexit would be a major issue, probably the major issue. That in essence would serve as a second referendum, and if anti-Brexit candidates did well enough, parliamentarians would have cover to go against the previous expression of the public will.
I give that path out of Brexit p = 0.2, with another p = 0.1 for “somehow Brexit just doesn’t happen.”
Addendum: The final word on Brexit rights may be held by…the European Court of Justice.