https://marco.org/2011/01/18/apples-been-here-before-jobs-missed-most-of
Apple’s been here before. Jobs missed most of 2009, and when he returned, it was a while before he got back to full time. The product cycle continued. Existing products were improved. New products were released. Future products progressed in development. Was it the same without him? No, of course not. Did the company function just fine? Yes.
— John Gruber on Steve Jobs’ medical leave