The statement in the article "The problem for businesses now will be in obtaining copies of XP in the future" is incorrect.
Computers purchased with Windows Vista Business (as appropriate for a business computer) will have downgrade rights to go to XP, or heck, even W2k if so desired.
The way to do this is through Microsoft's volume licensing programs, the least of which, a business can get into with a minimum purchase of 5 licenses. Given that server cals are below $30.00, people can always use another copy of Office or two, it's very easy to get to 5 licenses!
The biggest bonus, is that once you feel confident to move to Vista, you can just use a restore CD and bounce that system back up.
You do NOT get this benefit if you purchase a PC with XP installed, to then move to Vista you would have to purchase the Vista upgrade.
It is very short sighted to purchase an XP pc today, when a business could easily get a '2 for 1' deal by starting with Windows Vista Business.