I don't know if there will be an October update (hopefully) or it will be in 2013. What I begin to be sure is that this one will be the LAST one. Whether it is in October or in 2013, I'm afraid there will be no more iMacs after that. The company (maybe the whole computing world, as a matter of fact) is turning into mobility.
it wont be the last one clearly you dont know what youre talking about.