A couple for days ago I came across a TechCrunchIT guest blogpost 'Welcome to Web 3.0: Now Your Other Computer is a Data Center' by Mark Benioff. He is right on many points, but there is more.
As an ISV I can tell that the focus on customer value is always the most important aspect. In the past all software was developed in house, but this changed into assembly of solutions from standard components. The Software as a Service trend is only a logical extension of this trend.
There is however more, Web 2.0/3.0 allows for much better collaboration between companies that traditional Client/Server doesn't allow. Today the majority of all IT spending goes into integration between systems, because it's complex and there are many (On Premise) systems to integrate. For this reason system integration is not accessible for small and medium sized customers.
However, Software as a Service and the consolidation of cloud infrastructures is reducing the number of systems to integrate and eventually the integration will be offered as a service too. This makes system integration accessible for small companies too and thus changes the way we do business.
It's evident that the role of the ISV will change and needs to adopt their business models.