Feige said: "Iron Man 3 doesn't feature any of the other Avengers, or Nick Fury showing up, or any of those world-blending conceits that the Phase One films had."
That definitively rules Szostak out as Wasp, an Avenger.
Doesn't mean Szostak isn't playing a traditional Iron Man villainess, though.
Not so fast. She could still be Janet Van Dyne and not yet Wasp. It is a fine line, and not likely, but it adheres to Fiege quote above in the literal sense.