Whilst it is true that the risks with XP are increased when Microsoft support finishes there is no need to panic if you take reasonable care. Remember that a certain amount of hype over the matter is in the interest of those who want you to purchase their products so there may be a little over egging of the pudding.
"reasonable care" alone can't do anything against security holes. However, you're right in the last statement of this part: especially AV companies and supporters of them tend to posh things up, trying to ensure you, that their "internet security" and other "security software" will protect you from any malware.
Fresh install > add Deep Freeze and Data Igloo > end of problem . Nice new system every time you boot up, no malware, no defragging, no maintenance ............ just enjoy using your system.
On which basis can you ensure that the machine isn't already infected when you set it up or when you would use it with network access after end of support? Just because your Antivirus and any other security software you're using for system check doesn't find anything and you don't see irregularities in network traffic or CPU/GPU load or any other weird behavior, it doesn't mean that you are "virus free".
Heck, even an
outdated network printer firmware could be used for exploits even for
taping your VOIP-phone (if you want to watch the video without logging in, you can do it
here, the video itself on the bottom of the page is in English).
Also, Windows does the defragging and other maintenance tasks automatically.
I think the thought process is that even if they no longer issue new OS patches, it is in everyone interest to prevent known mass infections aka botnets.
Right, but it should be regarded as the final grace period to migrate to another OS. If someone has something like a 10 year old computer on which even Windows 7 doesn't run, with about 350-400 dollars or 250-300 euros, he or she could either get a much faster office computer with SSD included or a good tablet which would still be faster with way better energy efficiency than the "museum" hardware he or she is currently using.
There have been many warnings already that the support for Windows XP will end eventually, so if those years haven't been enough to gain at least around 410-460 dollars or 290-340 euros for a newer computer with Windows 7/8.1 OS or less for a tablet, you could at least afford a 4gb usb flash media or a blank CD/DVD to get a still supported (live-)Linux for internet access.
If these previous updates are going to disappear then what are the options?
For the sake of minimizing the risk of being part of a botnet and thus an inconvenience for most users: please either plug it off from the network or switch at least to Linux as a secondary (live) operating system if you need internet access. Even an exploited website or part of it loaded by other websites (for example pictures/ads) could target exploits and it's most likely that the number will increase the longer a system will stay unpatched.