Though I am an ardent fan of SOA and the potential impact it could create on the IT and Business, I should acknowledge that there are significant complexities involved in implementing SOA. Zapthink partner David Linthicum talks about it persistently in his blog. SOA makes tall promises. However, to realize the promises, it requires skilled SOA architects/designers, business consultants, sponsors and above all patience. :-)
Having said that, I should say Virtualization leads the game in terms of realizing the promises and achieving the benefits. Here is a reference. PC Quest has recently announced the Top IT implementations for the year 2008 and I couldnt find a single SOA focused project. Almost all of them are pointed solutions that are targeted towards solving a specific business problem. Am not saying that pointed solutions are bad. The point here is SOA has not been mentioned as a key stragic enabler in any of those implementations.
However, I could see a virtualization success story. ICICI bank has recently completed the enterprise server virtualization project and this project has been selected as one of the best implementations. More than the project, the metrics made me to say Wow!. Here it is - The bank was able to condense more than 550 servers in about 43 servers using VMWare Virtualization Technology. This is a strong metric that speaks the benefits of Virtualization.
Virtualization as a technology concept is slowly making in-roads into the industry and Even conservative IT shops are bound to invest in this technology for the solid proof statements that can be seen around the industry.
There are plenty of SOA case studies as well. Am not denying that. However, I strongly believe that virtualization has a direct impact on the fundamental economics of an IT shop and hence it succeeds, whereas SOA has an indirect impact via the business solutions and the actual architecture that gets implemented.
So My suggestion would be - Invest in virtualization today to save money so that You can invest in SOA tomorrow! :-)