OK, so it's a little link baiting, but... ZDNet has just posted an article about Your perilous future on Windows XP. Basically, Microsoft will stop supporting XP on April 8, 2014. This means no more security patches, no more malware checks, and no more holes plugged in Internet Explorers 6 & 7.
Yes, there are still people using Internet Explorer 6 & 7. Why? There are large organizations (public and private sector both) that invested a lot of time, money and resources to put XP on their desktops to begin with. They then wasted even more money developing browser based applications that only ran in those browsers.
So, here's what's going to happen. MS will EOL XP, and IE 6 & 7 with it. (Definitely 6, and hopefully 7...). The day the last patches are released, new zero day exploits will come out that will never be patched. After the initial pandemonium, organizations who have not upgraded from XP will either A) upgrade right away, or B) start using Firefox or Chrome. Many of them would also start spending mad resources to upgrade their application code to work in browsers other than Internet Explorer.
Where this is going to be felt first, hardest, and likely the slowest to respond, will be within the finance and government sectors. These are the areas that should be the most secure, but are also the tightest on the purse strings. It will probably take some major intrusions, crimes, and data loss before they finally begin to respond appropriately. Even then, it will probably take an Act of Congress, which means it'll be even longer.
Now, will all of this come to pass? I don't know. That's what it looks like in theory. They all though Y2K was the end too, and it wasn't. I do think that this is a much bigger threat, on the grand scale of things. Guess we'll just have to wait and see...