It has been a huge endeavor to get Windows Vista out the door, but according to Microsoft CEO Steve Ballmer, there's "plenty more where that came from.” Sure enough, there is more to come starting with Vista’s first service pack which should be released before the end of 2007.

There has been much speculation in the industry, however, that Vista (and similarly Office 2007) would be "last of its kind.” With the rise of the Internet and the "have it now" aspects of online applications like Google Docs & Spreadsheets and Google Calendar, many experts believe that Microsoft's model of doing business is going the way of the dinosaur.

"Microsoft made Vista the old-fashioned way, as a single packaged product that it puts on a disk so users can buy it in a store and load it onto their computers," said Dean Takahashi of the San Jose Mercury News.

Takahashi continues with this scenario, "By contrast, rivals such as Google are creating spreadsheets and browsers that you simply download from a computer server, which delivers what you need to your desktop as you need it. If Google follows through with more offerings of free, ad-supported software over the Internet, Microsoft won't be able to charge a premium for its operating systems anymore. Nobody will need its big upgrades anymore."

The Windows operating system has grown more and more complex requiring an immense amount of manpower and resources. Vista has been a 5-year endeavor and Takahashi estimates that over 10,000 employees working on the project have cost Microsoft over $10 billion USD in payroll costs alone. “That has to be close to the costs of some of the biggest engineering projects ever undertaken, such as the Manhattan Project that created the atomic bomb during World War II,” said Takahashi.

"The current, integrated architecture of Microsoft Windows is unsustainable - for enterprises and for Microsoft," said Gartner analysts Brian Gammage, Michael Silver and David Mitchell Smith.

Despite the skeptics, Microsoft is confident in the viability of the Windows platform. "We've got a very long list of stuff our engineers want to do, a long list of stuff all of the companies here want us to do," he said. "There are so many areas where we need innovation," said Ballmer.

When it comes to future variants of Windows, Fiji will be the first dramatic update to Vista and will arrive sometime in 2008. According to various reports, Fiji will include WinFS, better integration with Windows Live services, native HD DVD support and enhanced speech recognition, among other things.

Vienna, which is even further out on the timeline, is expected to be a more radical departure from what we all consider to be a "traditional Windows operating system." Although not much is known about this release, the leap in design/functionality is rumored to be akin to the OS 8-9 to OS X transition.