Downwards compatibility during long time development
Larry Osterman’s post explains that there will be no new kernel since it would break downwards compatibility. He mentions an example where Microsoft dropped support for NT 4 audio drivers in Vista and immediately was called by customers who complained about not-anymore working audio software - although the support officially was dropped 1998 anyway.
First of all this example shows pretty well why it makes sense to use Free Software for your core applications: in the worst case (the vendor goes out of business) you can still pay someone else to make changes you really need. In this case the call center could just pay a developer to alter the audio core of the application to use the new ones.
Nevertheless the question remains if something similar could happen with Linux.