Linux has some application areas that will certainly grow regardless
of what MS does.

Senior citizens want an inexpensive operating system that runs on
inexpensive (sometimes hand-me-down) computers and can be maintained
without relearning a radically different version every few years.
This is one area in which install fests can expand Ubuntu use.

People like

http://www.olpcnews.com/

frequently state reasons why children's education needs a flexible OS
that runs on less than cutting-edge machines and can be maintained in
remote limited-budget areas support people must learn from readily-
available GPL documents.

And, of course, cottage MCU (microcontroller) application developers
need an operating they can embed without bloating product cost.