Frankly, I wouldn't place a lot of my money on Weiner's political longevity at this point -- given that his party leaders are cutting him loose and a mounting level of Ethics and even legal jeopardy. But Cantor's statement actually makes me think he's going to hold on longer than I might have thought.
The classic example of this comes from back in 1998. There was a relatively brief window of time after the Lewinsky scandal first broke that all bets were off. Probably most people assumed the president would have to leave office. Regardless, no one was making any predictions. And Republicans -- while clearly overjoyed in political terms -- kept their heads very low. You could tell that window had closed when the president's Republican opposition started going on the airwaves attacking him over the affair. The key is that the opposition makes a political calculation that the downside of pushing is outweighed by upside of forcing a resignation or at least getting mileage out of demanding one. Once Republicans started hitting Clinton on the Lewisnky scandal openly that's when you knew he was probably going to survive.
This is by no means an absolute rule and Weiner could be out tomorrow. But that's what Cantor's statement tells me.