I wonder if the predictions are numbered in order of Gartner's confidence in their predictions, or the importance of the events should they take place.
In any case, this would be a huge change in the IT industry, touching everyone from applications vendors to systems integrators and the channel.
I think 2011 is too soon for this to happen because there are so many systems out there already, and people aren't going to be ripping and replacing in this economy. If we weren't in a recession, I'd say that makes sense.
But traditionally, people swap out equipment or make new investments every five years or so because of accounting principles--not real business need and not because they've got money burning a hole in their pockets.
And while there is much lower up-front outlays for getting cloud computing, it's a fallacy to say there are none. No CTO in his or her right mind is going to sign up with a SaaS vendor without also having some in-house storage and back-up as part of a contingency plan.
SaaS is no longer the great unknown scary thing it was even two years ago, but it has entered the murky waters of enterprise detente. "Trust but verify"--or in this case, "trust but have a fail-over."