Test drove the new A1 at the weekend it's pretty nice. There won't be an S1 but they will launch a 2.0 TFSI variant next year which will match the Polo GTI for power.
My local dealer also mentioned the RS1 rumour, will be very cool if true! Proper pocket rocket
There is indeed no S1 coming, but the RS1 is on the way with around 320-350bhp. However it will be stupidly expensive - think £40k - to offset the development costs.