Unfortunately cortana will speak pt-br because it is official variation chosen by Microsoft. Pt-BR is more spoken and learned around the world.
We have about 200 million of Pt-BR speakers and about 12 million of pt-pt speakers.
did you try to use voice command in Windows Phone 8 using pt-pt? It doesn't exist only pt-br is available.
Yes I tried in pt/br, but she doesn?t understand me well. there is no pt-pt voice I think...