That seems likely to me. I'm betting that it was only announced as an interim move, to prevent the utter stock chaos that would result from him announcing his retirement.
He's gonna be a hard man to replace, both within the company and as the external face of Apple.
If Jobs is only taking leave, then Apple will survive fine. If this turns into something more permanent, there needs to be a visibly strong leader appear, someone with a force of will and personality to be the charismatic asshole leader type, someone with a strong vision for the future.