Worst possible ending IMO...
Would be Jon dying and Dany being pregnant with his child and serving as regent until it came of age. That would be a major cop-out for many reasons.
Jon was dead and came back. I would think he was sterile at least now.
Dany was supposed to be sterile until they implied last season that the witch might have lied. Which would mean that she was screwing Daario for like 3 years without getting pregnant and would be knocked up her nephew after like 2 times.