Bin Laden became the modern day Dr No, Blofeld and Dr Evil. A figure seen / portrayed as a global terror who belongs to no state organisation or indeed state. Thus post 9/11 he becomes public enemy No 1. Without Bin Laden (say the above scenario or he dies prematurely), many of the real and perceived grievances within the Islamic world (Iraq and other parts of the Mid East, N. Africa, Indo-Pak border, West Bank & Gaza,) will still exist.
Whether another individual could galvanise support as Bin Laden did is the question. Bin Laden came from a wealthy Saudi family, seemingly turning his back on such opulence which turned him into a folk hero of Robin Hood proportions to his followers and admirers. We may see more sporadic attacks without Bin Laden but perhaps nothing like 9/11.