This is very normal. I got several such response from profs at UBC, UVic and others. I think you will have big chance. If he had found anyone, he would have rejected you by now. My guess is that he wants to hire the other guy who's also waiting for another better choice. So, after a while, your potential advisor would contact you. You may send another email to represent your strong wish to work with this advisor. It won't hurt.