I am not worried especially after seeing the massive new product launch by Apple last week. Apple destroyed the competition in every category - tablets, desktops, and laptops. That new iMac is gorgeous and the MBP's are the best laptops in the business. Further, look at the feedback from Windows 8 - why am I not surprised?
Apple has nothing to worry about because the competition continues to make ugly and buggy products.
Short term, absolutely. But Apple's long-term health depends on it being excellent, not marginally better than Microsoft.
Maybe Forstall had become a net negative inside Apple. Only time will tell. Apple's dominance, however, is based a lot on what came out of NeXT, and Forstall was key to getting that to run on Intel and on iOS devices. That is what I am nervous about for the long run.
Having something like OSX to exploit at the perfect moment in time and marry it to portable hardware was something no other company had. If that was a unique moment in time, then Apple was lucky and it may be reduced expectations from here on out.
So much pressure must be on Ive now. If he wasn't planning a major overhaul of Human interface, then he must be now because that's what everyone is expecting.