Yang Zhenduo was 9 or 10 when Yang Chengfu died. He is in his eighties now. There aren't too many of Yang Chengfu's students left active. Their students are still out there, I believe. Here are some well known ones:
Li Chun-nian (Li Yaxuan)
Li Yaxuan's students are definitely still active and I have a book by one of them.
Cui Yishi's grandson is teaching, I think, and no doubt there are other students in that lineage. You really just have to look.
Tian Zhaolin's son Tian Yingjia has 49 disciples and has taught some 500 students in all, according to this site: http://www.art-of-energetics.com/New/tian_zhaolin.htm
[This message has been edited by JerryKarin (edited 12-05-2007).]