I do believe that Midna and Link did eventually see each other again. It was known that both worlds were connected when it was twilight in the normal world. Knowing how close they were, I doubt that both of them would just not try to at least stay in contact. I feel like somehow, some way, they did end up contacting each other and maybe even found a different way to see each other. As I said the two worlds are connected, so it is a possibility for there to be such things without needing the mirror.