According to those estimates, the margins on AWS will actually increase from ~11% today to ~15% in 2014. It seems more likely that cloud computing will trend towards commoditization, and margins will collapse over time. Amazon is trying to preempt this with proprietary technologies like SimpleDB and SQS, but I question whether companies will opt in to that kind of vendor lock-in en masse.
I hope they'll still continue to improve on EC2 / RDS.
Fear of vendor lock-in is the reason I'm trying them out for my current project instead of Google's App Engine.