The reason why there is some worry about geeting quick ecu flash HP out of the 2.0T of the ST is the following:
"Matthias Ton, stated that the 2.0-litre EcoBoost engine used by the ST was close to its power limit without significantly upgrading its fuel system and turbocharger"
-Top Gear UK-
In order to go past the stage 1 level of modification on a GTI, which is similar power in the ST, it is recommended to get a new downpipe, catback, intake, and intercooler. I would also suggest a HPFP upgrade (FSI motor not TSI). The next step is a new turbo. Stage 3 w/ turbo does bust out over 400 HP and 400 ft/lbs of torque. All in, the parts are $6000-7500.
Its unknown what aftermarket support with ECU flashes and the like will be out there for the ST. Hopefully there will be a $500 chip that takes it up 30hp/40ft/lbs of torque. If not, swaping turbos, fuel pumps, and exhaust isn't always cheap.