Game of Thrones season 8 episode 4 "The Last War" will feature Daenerys Targaryen finally coming on terms that Ser Jorah Mormont is no longer with her and she has to march King's Landing with her remaining allies. Jon Snow will probably accompany her but as per a recent fan theory, she will be betrayed by Tyrion Lannister.
Game of Thrones season 8 showed reunions of several major characters. On one hand, we saw Arya Stark reuniting with Jon Snow, and then we saw that emotional reunion between Sansa Stark and Theon Greyjoy. But there was a moment in episode 2 "A Knight of the Seven Kingdoms" where we saw Tyrion Lannister approaching Bran Stark. Their conversation by the fireside was not shown but it looked like the duo talked about several instances for example how Bran became Three-eyed-raven and how Jon is actually Aegon Targaryen.
"Bran told Tyrion who Jon actually is and it will be the driving force behind him switching sides. A lot of us couldn't see Jon releasing the information on his own to get the throne. What if Tyrion tells the world that Jon is the true heir because he doubts Daenerys' intentions or honor! This would force Jon into a situation of conflict," writes the fan on Reddit.
Since Jon Snow is Aegon Targaryen, he is the true heir to the Iron Throne. Even Daenerys Targaryen holds no right to the throne till Jon is alive. At the same time, Tyrion knows very well what is going on between Jon and Daenerys and back in season 7, we learned that Tyrion was heartbroken after seeing Jon Snow knocking at Daenerys Targaryen's door in the middle of the night.
Furthermore, few of Tyrion's wrong decisions has cost a lot to Dany. Her ordering her own Hand to stay in Winterfell crypts during the battle of Winterfell could suggest that she has lost all faith in him and would try to push him further away in the remaining two episodes.
If Daenerys will ask Tyrion to stop serving her as her Hand, he would simply reveal to everyone that she holds no right to the throne as it is Jon Snow who is the destined King of all the Seven Kingdoms. If Tyrion does that then it will come as a blow to Khaleesi who has lost everyone she has ever loved.