Should I worry that my Microsoft programming skills (C#, .NET, WinAPI) will be obsolete in a few years, because everybody will be using Mac OS X, iPhone OS or some other Apple-originated OS?

According to reuters, Apple has now bigger market capitalization than Microsoft. I know there is probably huge speculative bubble around Apple's shares, but just look at this graph (taken from business insider):

I also know Windows have currently 90% of the OS market share, so we (Win devs) should be OK for a few years, but who knows, maybe in 10 years, it will be just 40%, and 0% on mobile phone OS market.

Personally, I'm not much worried, because I think Microsoft will fight hard for their desktop OS market share, but I'm interested in your opinions.