The title is not an accurate statement. JQuery 2.0 will not support Internet Explorer 8 or below. While IE 9 does not run on XP, other modern browsers such as Chrome or Firefox do.

And JQuery 1.9 will still support all the browsers the current core does, with the same API and features of 2.0. 1.9 will just be "heavier"

Misleading as shit. Recent versions of good browsers still work and will work on XP.