Yeah, Dany and Jon are most likely going to have a baby. It's interesting because Daenerys' stillborn baby with Khal Drogo apprantly had monstrous features, scales, and leathery wings which implies she can only birth dragons. If Jon really is a Targaryen with Dragon blood in his veins - their child will most likely have dragon-ish features, such as distinct eyes and sharper teeth, but minimized thanks to Jon's blood not being tainted by a witch. Their child would be an absolute beast (as a crown prince/princess, and not literally). Also, the scene where Longclaw opens his eyes is a nod at The Battle of the Bastards where Jon climbs out a horde of people and gasps for air and when he's resurrected by Melisandre - both are really similar to where he comes up from under the water. All three scenes represent a sense of rebirth/enlightenment in my opinion because there's a dead dragon in the water with Jon when he's down there under the ice. This could mean his Targaryen blood might've awakened, and his Valerian sword could have responded to it. Just a hunch though.