There are relevant assets which can be purchased, such as the main thread, GitHub repo, web site, etc. That's generally what people mean when they speak of buying a coin. Doing so conveys a great deal of influence over the direction and development of the coin, although it isn't definitive as the community may choose a different direction. If the direction proposed by the successor is reasonable (e.g., actually involves some forward progress on development, including important long-unfixed bugs; lacks retarded ideas like hard forking to dilute supply and put 50% of stake into the successor's pocket, etc.), there is a good chance the community would follow it.