The woman who would probably take over from him is Diane James, I watched her on a debate with a bunch of East London students. It was a very hostile group of many ethnicities, as you would expect, and I thought considering it really was a no win situation, she did very well.
She is no Farage, but then again he is up there with the best orators right now.
So UKIP will carry on regardless, it will be a massive blow and set back but I think the foundations are laid and they are here to stay.