The 7 Heroes of Wudang in HSDS are among the most talented in wulin. Most, if not all, of the 7, had invented their own martial arts -- a sign of great talent. Zhang Sanfeng praised Yu Lianzhou's invention as a masterpiece. They also learned Great-level martial arts from a Great. And yet, it seems they were still short of achieving Great-level.
They lacked a freak accident or a special boost. But then, I don't think any of the original Greats was known to have received a big boost. So it is still possible to reach Great-level by the "normal" route.
ROCH Great-level is out of the question for them, but I wonder if the Wudang Heroes have a shot at reaching LOCH Great-level? They probably weren't too far behind by the end of HSDS. And, let's not forget an important feature of their orthodox internal energy, is that it improves FASTER as you become more powerful! So they should receive a significant boost from age 50+ till their bodies run out of steam. In particular, Zhang Cuishan, the teacher's pet, might have surpassed the other ones if he had a chance to live longer.