I seriously doubt that anything malicious will happen because even with the MS updates computers were still being infected by malware and it's been like that for almost a year.
The common idea is that malware authors are keeping their exploits secret or whatever until XP's End of Support. While this may be true, there is a far more dangerous problem in terms of End of Support. And certainly the idea that there is going to be a instant wave of exploits and XP computers will be compromised the instant support is dropped is silly. The real danger is not as easy to express in a sensational headline, so it's usually glossed over.
Windows XP is based on the NT codebase; effectively, Windows 8.1, Windows 7, Windows Vista, XP, 2000, NT4, etc. are all very similar, since they are effectively the same codebase (a succeeding version is not completely rewritten from the previous version).
Once XP support ends, XP will, of course, no longer be getting security patches.
However, later versions will. Malicious actors will reverse-engineer the patches provided by Microsoft for those later versions and determine what they fix and primarily what the security problem being patched is; then they will verify that the security problem being fixed was also in XP. If so- and chances are that a good percentage of security patches for later versions will be backportable to XP- that's a free exploit that will never be patched. This is worse than the current situation where those exploits are found either through intensive labour or by reverse engineering the patches and attacking only unpatched machines. Basically each update, patch, or hotfix to later systems will be a free exploit.
eg. let's say somedll.dll has an exploit that get's patched in Vista/7/8. Malware authors will find that patch, see what it changes in somedll, and find out exactly how to attack the patch fixes is made; then they will try it on XP.
if it works- free exploit. If it doesn't, move on to the next patch.
I had a message last week from MS that MSE would not receive anymore updates. That's why I switched to Avira. MSE will only update for Vista and Windows 7.
the MSE download is no longer available for XP, but it will receive updates.
Microsoft has also stopped providing Microsoft Security Essentials for download on Windows XP. (If you already have Microsoft Security Essentials installed, you will continue to receive antimalware signature updates for a limited time, but this does not mean that your PC is secure because Microsoft is no longer providing security updates to help protect your PC.)
from
here. Since it doesn't define "limited time" it a not-unreasonable idea to switch to something else.
