I was one of those surprisingly many people that voted yes. The reason that I thought that someone might eventually be better at Aikido than the founder was, is really just a matter of general life principle for me. I am 'n Physics student at University and we are taught the old theories of the old physicists. Then we are taught the less older theories and so on until after almost a lifetime you learn the new theories and the when you are really into your physics you write the new theories.
The reason I say all this is that I think Aikido can be compared to this. Every new student will learn everything that OSensei taught. Even so for a yodansha. But when you get very high up (like shihan level, and you are really very into you Aikido) you might get new insights into Aikido that OSensei might not have had and so the art can advance as a whole from the new insights the top practicioners have.
I realise though that none of this new insights will be possible without OSensei's training to "stand on"