nope, i can assure you 100% there isnt even an RS3 sketch at Audi, nevermind prototype.... Audi would hardly keep something quiet to sell more cars of another type...
think about it like this... how much do you think an RS3 would cost... £32-33k then add some extra's.... your at £35-37k for a 3 door hatchback... what power would they put as standard... maybe 320bhp?
It just doesnt stack up... and thats why Audi have no intention to make one, I asked the question at Audi headquarters, and that was there response, there is no room in the Audi range of offerings to support the building of such a car!
I know its a shame, good knows I'd have liked to try justifying the spend, but its never gonnna happen... and IF it did Audi wouldnt be keeping it hidden, they'd be shouting it from the roof tops!