Nobody knows for sure who will sit on the iron throne. There are many characters who can sit on the iron throne at the end of the series, but currently, the one sitting on the iron throne is Cersei Lannister after her sons Joffrey and Tommen Baratheon tragically died.
Fans can only speculate who will ultimately sit on the iron throne, but Game of Thrones is filled with twists and turns, so nobody can truly confirm who will eventually sit in the throne. However, Jon Snow a.k.a. Aegon Targaryen is the rightful heir to the iron throne so it is highly likely for him to take over the Seven Kingdoms if he will not die in the books or in the series.
