The system that I train is rare, with very few people teaching it in the world, much less in my area. In my estimation, most of the few people who do teach it, do not do so very well. I am extremely fortunate to have the teacher that I have.
I cannot imagine going outside of my school to find another teacher, in the system that I train. If Sifu passed on, I would continue to train with my sihing, my senior classmates who know more of the system than I do. Other than that, I do not believe that I would benefit from trying to find another teacher in my system. I do not believe I would find one nearby, and if so, I am doubtful that they would have much to teach me, at least in respect to quality.
I think it would really be up to myself and my Sihing to decide where we wanted to take things from there.
I have actually pondered this on occasion, and I think that even if I was not able to learn any more of my system, what I have is enough to be very effective and even "complete" in its own way. I have not learned the entire system, but I've learned enough to understand how the system works, and that is what is important. So I can be complete, as far as practicing Tibetan White Crane, even if I haven't learned the entire system. I'm not sure if I'm expressing this in a way that makes sense, but I'm trying...
The way Sifu teaches, he encourages us to learn and really make the system our own thru properly understanding it. That understanding is where the real lessons lie, not in the curriculum itself. Once you really understand what you have, the rest of the curriculum becomes less important, as it is simply a tool to help you understand how to do things, rather than a list of techniques that you "need".
If I decided to pursue another system, then obviously I would look for a new teacher.