4K Sector Drives are on the way and will become standard by 2011. Windows XP users are likely to face problems accessing them. Even if they do manage to access the drives using built-in emulation software, accessing a 4K sector HDD in 512 byte mode will slow the drive down significantly. In addition, XP users will run into issues with disk utilities such as formatting and disk cloning software.
If you're using Linux with a kernel released after September 2009 (like me), you won't need to worry about anything.
For people who're still using ancient Windows XP, anytime would be a good time to switch to Linux. I personally recommend Ubuntu.
Drobo, XP Users: Beware of 4K “Advanced Format” Drives!
Hard drive evolution could hit Microsoft XP users