It seems the investigators are deliberately not speculating in public about motivation of whoever forced the plane off course.
There might be more information at the next press conference, but I think the tone of the PM's comments means that they'll be very careful not to say anything that has not been confirmed.
The news is giving a whole list of countries which it could have overflown. All will be asked to share data that might help spot MH370. The one I think where it won't have gone is Afghanistan, as that's where the likelihood of diligent 24/7 real time monitoring of airspace is greatest, and chance of non-communicative plane being shot down in unpopulated area the greatest. (And whatever the motive might be, I really wouldn't expect it to be a wish to be shot down over Afghanistan, as the world already knows that's what'll happen there).