If I recall, GM Lim Hyun-soo has never been presented as the next 'Doju-nim' which is a very specific title for founder (or successor) of the art. If I recall, there were several people who supposedly were offered and/or given the title the 'Dojunim', including GM Chang Chin-il and Choi Dojunnim's son (and seems like maybe two others). The problem is that Hapkido has been pretty splintered off in a whole bunch of different groups that no one is really seen as the 'formal inheritor' of Choi Yong-sool Dojunim's system. Many people look to GM Ji Han-jae as the person who has really spread the art and stands among the very few who could be looked at the 'head of Hapkido'. (Please note I am generalizing and not trying to stir up a wave of controversy). A mere scratching of the Hapkido forest will show quite a few people of various lineages who have carved off their own group and become 10th dans (generally without the title of Doju) GM Lim Hyun-soo is recognized as one of the very few people to have trained directly under Choi Yong-sool Dojunim and been awarded a 9th dan from him, making him pretty much the man with the highest rank from (and most training under) Choi Yong-sool Dojunim. I don't think GM Lim has ever claimed to be 'Doju(nim)' nor represented himself as anything beyond a 9th dan holder under Choi Yong-sool. That he is a 9th dan under Choi Yong-sool Dojunim holds a lot of weight compared to the others who were offered the title of Dojunim, since they didn't have the rest of the corresponding rank directly from Choi Yong-sool Dojunim and the time in training under the founder. They were offered the title and theoretically a 10th dan without necessarily having the rest of the ranks directly from the founder.If anything, then GM Lim Hyun-soo would stand to make the best case for teaching 'Hapkido' the closest to what/how Choi Dojunim taught. My apologies for any errors... I am 'shooting from the hip' and would need to take a look at some historical sources for more specific details.