I have heard Shoji Nishio Shihan say, that he believes that each 'generation' of Aikido-instructors will find ways to parse on their knowledge faster than they learned it, so that each new generation will be able to reach new hights in ability.
Whether or not O Sensei's skills will be surpased is in my view a question of definition. If we define Aikido as O Sensei's Aikido and the only true Aikido to be what he embodied then it is not possible to surpass him, as there will be nothing else than what he contained. If we accept that Aikido is in constant development (which I believe) and that everybody has their own Aikido and each person doing Aikido is unique then the matter of who will surpass who in skill is of little or no matter.
As you might have guessed i voted 'I have no idea'.