According to W3C statistics for May 2014, XP is still number two OS, with almost 11% of computers running it. It's anything but dead.
IMHO, end of support doesn't mean that much. I've seen dozens of machines that were fully patched and still ended up full of malware. On the other hand, at the risk of sounding like a daft caveman I'm going to say that on my old computer I'm still running XP SP2 that only has about a dozen critical security patches applied. I kept Automatic Updates service disabled. I'm scanning my computers regularly with DDS, OTL, Malwarebytes and others and in last 10 years I've only had few minor and one serious infection.
My point is that regular updates can't stop users from getting all sorts of malware on their computers. That being said, I think update are still important.
One issue you haven't considered in this topic is hardware. In third world countries such as Serbia a lot of people are still using machines with 512 MB of RAM or less. One of the government agencies here has a print server with 256 MB of RAM and it has XP with no antivirus. We tried installing a few supposedly lightweight ones, and we disabled everything non-essential, but it was just too slow with any AV. This government agency struggles to obtain monthly supply of paper, so new hardware and new software licences are definitely out of the question. They are going to keep on using XP machines for a long as the hardware lasts. According to their accountants cleaning up malware is cheaper than new computers.