@deiruch: Most companies upgrade system with hardware. With OEM suppliers banned from providing new OEM WinXP systems, the market share is expect to shrink within 3-5 years. (I heard many companies bought downgradable models on the last wave, so make it this long)
Btw, lots of hardware vendors have stopped to provide WinXP drivers. Companies will have to move on... WinXP is not like Win9X which you could more or less make it work with only generic drivers.
OEM buys make no difference. If the company has a volume license, they can continue putting XP on new machines as long as drivers exist for the hardware. With companies moving towards VMs and thin clients, it makes it even easier to stay on XP.
As much as I wish my company would move off of XP, there is no good business case for it. We'd need to test our huge catalog of internal software, purchase upgrades for another piece of software we use (and spend time and money to test it against government regs), replace older PCs with hardware that can't handle Win7 (some of our PCs are 15+ years-old), and put a massive training effort into educating our 1500+ users to use the new OS (they are not tech-savvy). It would mean at least a solid year of effort and hundreds of thousands of dollars.
And evild, you were off by a version for your non-XP software. IE8, VS2010, and Office2010 all run fine on XP SP3. The just released Microsoft Flight runs on XP SP3.