Right, so they're doing fine now - and they will be doing fine for the near future.

But no product lines last forever - even Windows is bleeding market share, and upgrade rates are dropping like a brick. It seems a lot of people are happy with Win7 (or even WinXP) and not moving.

This strikes me as a Blackberry situation - market leader by a mile, but attempts to modernize and develop the Next Big Thing have all failed. They have enormous momentum and can coast for a long time - but what happens after? RIM failed to react to changing markets due to iPhone/Android, and arrogantly threw around their (momentum-based) sales numbers. Then those dried up.