I would expect a slight numerical gain, not enough to make a real world difference but enough to say "its up on power" (if you don't spot how the car is heavier...)
Radically more, nope and purely because of emissions control - VAG and everyone else need to reduce emissions not start making things more polluting. So some new emissions control measures and a slight power increase which overall drops the emissions is what I expect. The new measures wouldn't counter a massive power increase, so it will be for Top Trumps players and VW Marketing only.
"The new Mk8 GTI - more powerful and greener than any GTI ever!" will be the advertising slogan no doubt.