Melissandre said to Gendry that he would make kings rise and fall. The leech magic she did using his blood made Robb, Balon and Joffrey fall, which in turn of course made Jon, Euron and Tommen "rise" to fill their voids, but maybe Gendry will play a more active role in making kings rise? His hammer was also decorated with the Baratheon stag, which I think is quite symbolic. He will probably turn out to be very much like his father.
In addition, Arya said to Gendry that she could be his family before he was brought away by Melissandre. He replied that she would be "his lady". Marriage?