Think the left/right sentiment is more about that this is just the way things usually settle, not the way they have to be. You can have aphasia in non-dominant hemisphere strokes, aphasia is also not necessarily permanent in strokes. Recently I was linked a nature article where they rewired newborn ferret visual and audio nerves, they showed that the visual cortex was able to pick up and process audio input and vice versa. audio cortex was able to process visual input.