JSD has it right on the money.
The new lens will not be a waste. Really, the kit lens (I'm not sure what it is with the XS, but my 30d is an 18-55mm EFS) is a great starter lens. I still use it for most of what I shoot. But if you want to get serious into the hobby / art / business of photography you will have to expand your lens selection.
My only recommendation is to do research. If you're sticking with the Canon line make sure they are interchangable with the newer models (Canon is pretty good with backwards compatability . . . I have a 100-300mm EF lens from my Rebel Ti that works great even now . . . or as well as can be expected).
Before you start upgrading make sure you know your camera, and understand the elements of the Lens. Understand what your crop factor will do the focal length (the difference between Canon EF and EF-S), and what affect the aperture has on your photograph (Not just DoF, but speed). Also look into L series lens if you're making a serious investment.
Biggest mistake I made was picking up that 100-300m lens without research, probably wouldn't pick it up again, not because its not a capable lens, but because it didnt' do what I was hoping it would (and that error is mine).