I would be looking for an interesting PLUS for buying the BDs alreading owning the DVDs, something I did not have on the (European)DVD-set.
Although I am German, I like (watching) the Brazilian dubbing for TNG and DS9. Unfortunately, on the TNG-BD there was no BR-PT dubbing and the additional Japanese track donesn't do it for me. That's why I wasn't eager to buy them (I got S1 but not even watch all the episodes, only ca. 50% of it).
I would hope that they do some dubbing variation on the DS9-BDs. With BR-PT it would be an immediate buy for me. Furthermore, I think it's an general error to leave the Brazilian market potential aside.