Before the Island, Sun and Jin were having marital issues stemming from Jin's involvement with Sun's father. In the alt-timeline we don't know what choices Jin made yet that got him stuck in a closet so whether or not Sun supports him in this timeline is anyone's guess. I do NOT think that everything will end well for ALL characters, otherwise the balance between good and bad, right and wrong, and the course-corrected status of the universe is compromised.
If you mean "did they reunite on the island in the regular non-flashsideways timeline?", then no. Not yet. They are both in the same time again, and both are on the island, but Jin left the temple before Sun got there. As of "Sundown", Sun just left the temple with Lapidus and Ilana, and I guess Jin is still back in feral Claire's camp with a broken leg.