Pure conjecture. There is no reason to believe the results won't just be 2mpg lower than what you currently get. These numbers are 2 mpg lower than the sticker when you bought it. Mileage varies due to how you use your vehicle. Yes, a lot of TDI drivers have a driving profile which yields higher than advertised mileage. Some don't, and some are right on the original sticker numbers. At this point, here's no reason to be comparing your actual numbers to the "new" sticker numbers. I'm sure they are calculated in the same fashion as the original numbers. Do you really think they advertised the original mpg numbers low just so you would be surprised? No, they were based on average driver habits and driving conditions. TDI drivers just happen not to be average.
My pure conjecture is to expect similar, but slightly lower mileage than you currently get.
I have kept detailed records for 135k miles, so I'll have a great comparison to go by once the fix is done. Then we can discuss. And not after the first tank....