there will be a fiesta ST as well, and it will be turbo'd. so you can just stick w/ the OEM platform if you wanna, but it will be out next year and you will pay in the mid 20k range for it. for the money, you can easily go w/ an SVT, (no need to build the motor unless you want more than 325 whp/wtq. (forged rods stock) and the aftermarket is there and it will be cheaper! not to mention prolly handle better.
but if you want to stick w/ a stock platform, go for the fiesta ST when it comes out!
terminator v8 in an SVT focus (soon to be boosted @ 20 PSI with a 2.9 L Kenne Belle on Corn!!!
(750 rwp and low 10 second focus, here I come!)