Gartner recently published a prediction that we will see a rise in Cloud Service Brokerages (https://bit.ly/Rxn2F) as a result of the steam that SaaS is picking up. In fact Gartner has also predicted that "...worldwide cloud services revenue will surpass $56.3 billion in 2009, which is a 21.3 percent increase over the $46.4 billion generated last year. The market could reach $150.1 billion in 2013, Gartner said."
With this kind of momentum I suppose we are bound to see more vendors flocking to the SaaS model and with more options and choice, the brokers set up shop to aggregate services together for customers to make the choices simpler while adding some value. What I find interesting is that for it to work, the vendors must be very diligent in building systems that are multi-tenant, reliable, and leverage good open API's to allow data to move freely among systems and trigger functionality and outputs.