The three-door 2011 Audi A1 has just been revealed today and we allready have rumors saying that 3 additional versions will follow.
These would be the Audi A1 Cabriolet, S1 and Five-Door, versions that are intended to generate additional sales figures.
The first new version based on the 2011 Audi A1 would be the five-door model while the S1 variant based on the Audi A1 Cabriolet might be launched sometime in 2012. 
As we can easily imagine if the 2012 Audi S1 will be produced, then the upcoming Polo GTI will be one of its rivals.

Source: Autocar