A friend of mine works for SVT and he mentioned that a Supercharger was in the works, but nothing was final yet. The Supercharger they will be using is the same Eaton offered by Jackson Racing. You could always get a 03 with a discount and with the savings get the Jackson put on.
But this late in the game I would say they probably wont have it for 04 imo.
If they do go for it, look for 6 pounds of boost and somewhere in the area of 220 hp.
I've had my 03 SVT Focus since Oct. and it's been a great car and extremely fun to drive. As far as superchargers I know Vortech has kit. Over on focaljet.com there is a thread that a guy claims 260 fwhp with 9psi.