I don't think saturation is a problem. You can't get silk from a souse ear, or something like that. Apple's growth rate will continue to slow, but as long as it maintains it's competitive position it will still be very profitable and a good investment.

The Buffett investment (actually his sub-managers did the investment I'd bet) is an example of Apple gradually becoming a more attractive investment to value investors as it gradually becomes a worse investment to growth investors.