Microsoft are in a bit of a cleft stick (partly of their own making).
XP was a good OS for it's time but by default very light on security - it just isn't safe in todays world even if locked down.
The problem for Microsoft is that 500 million people are still running it for a multiplicity of reasons - they have old machines that won't run a more modern OS that they can't afford to upgrade (I'm looking at you Granny!), they can't afford and/or know how to upgrade and they may be running old applications that depend on XP's quirks.
MS, quite rightly, see no reason to keep on supporting an aged OS that stops people buying their latest offerings. And there are significant limits to securing XP on ageing hardware.
But the problem is that by stopping security patches they expose a very large number of users to exploits, which may well result in a huge number of pwned/botnet machines that could bring the internet to it's knees... You have to look at the larger picture.
MS is kind of damned if they do and damned if they don't!
A difficult problem!
Mac
[Add of course the seemingly unstoppable Mac onslaught, the slow evolution of Linux into more user friendly incarnations like Mint and Chrome OS, the remarkable rise of Android and Microsoft have a lot to worry about]
