Audi's own figure on their web site is 3.7 seconds, and I read two reviews (Autoblog and Jalopnik) that both said 3.7 seconds (perhaps they didn't actually get out a stopwatch and test it for themselves).
So Tesla only needs to get to 3.6 seconds to beat that.
The P85 already beats it, since the instant torque powers it forward especially at the beginning so by the time it hits 60MPH, the MS is ahead in terms of distance. There's videos of it beating Lamborghinis up to 100MPH, and even the GT-R is barely neck and neck with it, and that's a sub-3 second 0-60 car. If they're finally accepting 3.9 actual for the P85 and it's really 3.2 for the AWD, it's going to be a monster on the road. Pretty much everything else will be behind it under 100mph, and if the 2nd motor is geared differently as suspected, maybe it can keep pulling well beyond that.