mixture to be honest I think your screwed. It doesn't matter how much the IT pros go on about it there will be millions and millions of XP computers out there for years and years.
The rest of you take a clone of your hard disk as the last update goes through in fact make 2.
Keep your data on an external disk and have a plan how your going to clean it. Then if you get anything clone back the OS and clean the data disk before plugging it back in.
This is either going to go three ways.
1. The whole of the internet will be screwed when the next big one goes through and MS won't do a thing.
2. Same as 1 but MS sorts it out mainly because they are supporting huge corporate XP setups anyway.
3. Bugger all will happen.