That's going to be an interesting feature, really. I don't think there has ever been a crypto mixer that offered instant exchange integrated into the mixing process, to be honest.
Not that I know, but there are plenty of instant exchanges who are doing something similar and swapping Monero to Bitcoin and vice versa.
I could even argue that some of this exchanges
(they can be found on kycnot.me) exist longer and they are acting like mixers in this case, they don't charge high fees for this service so it won't be anything revolutionary if Whirlwind does this.