Microsoft clearly understands the importance of keeping their userbase patched up and has rolled out the fix for the recent IE vulnerability via Windows Update to Windows XP users despite claiming that no further updates will be forthcoming after April 1.
The reality is that the install base of legacy Windows XP systems remains significant and many larger organizations need a considerable amount of time to migrate. The decision to release this patch was a sensible response.
Mike the Crypto Goat 
If pushed I suspect MS will say it’s an “IE” patch not an “XP” patch.
However, the ludicrous charges MS quoted for extended XP support appear to be very flexable if customers basicaly say “no way”. Apparently one major MS licence holder started asking lots of migration questions of MS tech sup staff where the migration was all MS products they licenced not just XP to other non MS products which resulted in continued XP support being offered at just a percent or so of the original price.
The real issue is I susspect two fold. Firstly XP is the last MS OS that feels DRM free to business whilst giving the level of functionality required by business without pointless bells and whistles. Secondly XP runs quite well on hardware that is getting on for ten years old, and whilst not usually considered a problem for commercial organisations, the simple fact is with a recession since 2008 many organisations are not writing off functioning hardware, and thus following a “make do and mend” mentality.
Thus it could be said that MS have made a rod for their own back with trying to ditch XP, they have given dire warnings and backed off under commercial preasure several times and this may have actually convinced companies MS were not serious. The result is MS have probably chosen the worst time financialy to do it and are not realy offering a serious alternative (Win7 and subsiquent are not what most businesses want of an OS for many reasons).
I for one will not be ditching XP on my Air-Gapped development machines the same as I’ve not ditched Win2000, or NT –and still have Win3.1 knocking around– because I’ve still got to support embedded systems software and hardware I’ve developed that’s still in use on systems that I know will not have it’s OS upgraded or be decomissioned in the next decade unless the hardware can not be repaired…