You’re probably thinking Jon Snow is missing from this list, but his path leads north in season seven and not to the Iron Throne. Miniscule chance he’ll be ruling.
There are a number of other characters who could possibly achieve it. Tyrion Lannister is probably the most popular candidate, but as Dany’s Hand of the Queen, it’s hard to envisage a scenario whereby he becomes king. He’ll probably just remain her Hand. Sansa Stark will only get there if Baelish leads her to it and her sister Arya doesn’t seem the queen type. If Cersei goes down, her brother Jaime will either take her down or go down with her so you can rule him out and the Iron Throne is probably beyond the reach of any of the Greyjoy’s. Gendry is another possibility, but only because of his Baratheon blood.
Of course, this is assuming there even IS an Iron Throne at the end of season seven. It seems probable that its destruction will occur at some stage during the show. Could Daenerys burn it down?