donno I think pc sales have been stagnant or slight growth (very low single digit) a year. Mac desktop IIRC has been growing an order of magnitude faster
One question, what are the totals? The percentage is lowering but are the numbers declining?
heres the most recent figures I can find
-0.1% decline in growth, though mac numbers (which grew 12% are included in that) so PC numbers prolly shrunk by ~1% year on year, so yes windows PC numbers are shrinking
#3 well for indie game developers (like most ppl on this site), theres far more money in the android/IOS side of things than in the PC indie scene.
US numbers (in just under 4 years)
jan 2009 - windows (XP/vista/win7) 90.69%, apple (OSX,ios) 6.73%
nov 2012 - windows (XP/vista/win7) 76.87% apple (OSX,ios) 19.8% (OSX = 14.89%(*))
Yes MS (whom I think make the best desktop OS) are still king on the desk/lap/top, but the world is changing rapidly now, tablets,phones are ubiquitous. Perhaps the MS surface can change that, but I have my doubts. like the BBC website said so far reviews have been mixed the buzz so far is not there.
(*) i.e. the number of laptop/desktop mac's in the US has more than doubled in less than 4 years!
OK the numbers in china/india are like ~99% windows ~1% other, mainly due to piracy, but MS doesnt see much money from these pirated systemOS software