The Tories are going to have to jump one way or the other on this. They will have to say officially whether they think it will raise revenue or not. If they say they don't then they should have no problem pledging to scrap it. But if they say they do think it will raise revenue they will both undermine a key Right argument against higher taxes on the rich, and then have to decide whether it is a reasonable policy or not.
I expect them to not pledge to scrap it, but to play down its revenue-raising potential, which is obviously inconsistent. So it's a tricky call for them.