No-dogs(cats, apes, elephants, tigers, snakes, etc) do not have the same kind of vocal cords as humans with the ability of speech. All they will ever be able to do is what they already do, & having 3 dogs myself, I'd say they communicate quite well as they are!
Dogs probably don't have coherent thoughts that could be put into words. It would probably be just the four F's. "Fight!" "Flee!" "Food!" and, uh... "Fornicate!" although if owners had listened to Bob Barker, that last one will have gone away.
I don't think dog's brains are set up to speak--assuming you could bypass their problems being able to make speech sounds. Read some stories about cats being able to talk and it wasn't pretty. And what if they tell your secrets!!!! Squirrel!