Not disappearing any time soon.
"Windows XP's been without support for a month and a day now, but seems not to be falling out of favour any faster than happened when it was supported "
I recently happened upon an NHS Trust's IM&T strategy report that included the immortal line:
"Although we already support power users whose requirement is for the current generation products we are now actively working towards a route to Windows 7 and Office 2010. This will be achieved within the lifetime of this strategy."
The lifetime of the strategy was through to 2017, three years before Windows 7 itself hits the end of extended support. I suspect we'll see the same sort of reprieves for 7 as we saw for XP, because the disjoint between product lifecycles and the pace of change in large organisations looks likely to get worse.