Season 8, Episode 1 of Game of Thrones featured something fans have been waiting a long time for (other than those reunions, and Jon dragon-riding, I mean). Jon finally learned the truth about who his parents are.
It was A LOT for poor Jon to take in (even without the extra layer of the realization he's banging his aunt thrown on top). The scene ended before we got a good grasp of Jon's reaction beyond Shook™️, which begs the question: What will he do with the news?
Well, he is in love with Daenerys, which...complicates things.
It seems likely the revelation will cause Jon to pull away from Dany — if for no other reason than he needs to sort his own feelings out. But does that mean he'll betray her?
Perhaps, in the end, Jon will see a union between himself and Dany as the best bet for his kingdom (not to mention his heart). An added factor in all this is the idea that Dany is very likely going to be pregnant with his baby, if all the foreshadowing in Season 7 is anything to go by.
An even bigger complication is that, oh yeah, THE NIGHT KING AND HIS ZOMBIE ARMY ARE COMING.
As for how Dany will react to the news about Jon (if she does learn it) — she could feel threatened. Especially because her whole life has been defined by the desire for power, and specifically her quest for the Iron Throne.
Of course, this all depends on them surviving THE NIGHT KING AND HIS ZOMBIE ARMY.