Bore and stroke are to be increased to 83mm x 89mm for 2.0 liter capacity from the current 82mm x 85mm. Displacement alone is not going to help Mercedes reach their target so a larger turbo is no doubt in the cards. We would expect the heads, valvetrain, manifold, basically everything to get revised.
The other interesting tidbit is that it appears all wheel drive will be standard on these AMG models. These are almost going to be seen as a luxury WRX or EVO and no doubt will become some of the most popular Mercedes models to tune due to their entry level price point. Bring it on Mercedes!