"We will make a decision in the next few months and production takes two years after that," according to technical chief Ulrich Hackenberg.
"The TT is possible for expansion because it helps you stand out in 'inter-segment clusters' [Audi's phrase for white space]. We've done the concepts and now we must take the steps to look at production."
He said the Off Road was his favourite for the rationale of potentially boosting sales, but the Sportback was his favourite from a technical and design standpoint.
"Lots of people have already looked at the Sportback and said it's for them," he added. "People say they want it."
Hackenberg said that the MQB platform made it quicker, easier and cheaper to get more niche models to market, because the underpinnings are flexible and you can put a new "hat" on top.