Innovation has came before Jobs, and it will come after jobs. One man alone does not hold lock and key to something as big as innovation.
If Apple is the only company that can put a screen in 7 billion people's hands and home, how is this not a testament to greatness?
Don't be the next Steve Jobs. Be Tim Cook. Be you.
I think this fits with your larger point however: Ballmer was not a product visionary.
Every leader has their share of Missteps, and Cook has had his.
Forstall, from everything I've heard about him on The Talk Show, and on ATP.FM, was very Jobs like in his high expectations for people, his ability to drive creations through his singular focus. What he wasn't, was collaborative. This was okay in the Jobs era, when collaboration wasn't really needed - everything was an extension of Job's desires (which also meant that those things that were not, tended to be neglected - mobileme).
Perhaps, after reflection, I don't know if I would call Forstall a Cook Problem, so much as a resource that could no longer be effectively harnessed in the Cook Era. Or, perhaps, he was the DRI (Directly Responsible Individual), who had to take the responsibility for the Maps V1 cruddy roll out.
What we know for certain is that Apple can still _execute_ very well and stay competitive in a certain market. The latest offerings of Macs, iPhones and iPads are ample proof of that.
The question which is still unanswered is whether Apple, with Tim Cook and the other leaders, has what it takes to stay innovative. It's too early to tell, and I think it's certainly to early to write a book about it.
Since Tim Cook has gone on record saying that we will wee new product categories within the year, my guess is that we'll know for certain in 2-3 years time.