Ford may shock us, but I'd be very surprised if it came out in September at the same time as the rest of the new Fiesta range. From anything that has been said in the past, Ford have said it would be "soon" afterwards, but that has always been taken to mean sometime next year ie. spring/summer 2009. I'd imagine that they'd want to market the main Fiesta range, and then market the top model separately, although it could be the case that as with the Focus ST it's unveiled to the press around the same time as the main models go on sale.

The only reason I can think why they possibly would put it on sale at the same time is that they would want to use the ST as a marketing tool for the rest of the range.

Ultimately we're all just in the same boat of guessing at the moment, and will just have to see what happens.