So long as there are businesses willing to invest in the latest Microsoft blessed framework there will be a community of people willing to learn them and sell their skills to those companies.

For me, the real question is, why are business still willing to make investments in the latest Microsoft blessed framework?

Actually, I think since Longhorn there are signs that businesses are a bit more sceptical about these bold technology announcements from Microsoft. They used be able to pretty much control the weather but these days they have a hard time getting people to use things like Silverlight, WPF or XNA.

Their dominance is still strong in the enterprise though. SharePoint does not deserve the market share it has. But business are hooked on using the Microsoft tool for whatever it is they want to do. Need an intranet? Well Gartner says we need an enterprise CMS... so we'll hire our preferred Microsoft Gold Partner and give them a budget of 200k to build us a clustered SQL Server environment on which we can run some load balanced SharePoint app servers, all for a two step content approval workflow and a few thousand hits per day. Everyone in that process is too busy making a living to question the "we'll just buy whatever Microsoft has for X" assumption.