Dany will likely split her forces, with Yara and Theon going to the Iron Islands to reclaim it from Euron and then move to take the north, while she goes to the now mostly vacated Dragonstone to prepare for the attack on King's Landing, which would fit with how her ancestors took the continent long ago.
Cersei, with no allies left, will fortify herself on threat of total destruction of the city should it be sieged, since she still has all the other caches of wildfyre somewhere under the city. This will hold off any attempt for Dany to start her full invasion. Back in the north, Theon will have an issue of conscious due to the fact that Jon now rules the north, and the pains of his past actions will haunt him. I have a feeling he will either convince Yara not to attack the north, will bow out of the fight with Yara losing, or maybe even kill Yara to protect Jon and Sansa. Either way his will further stale Dany's attempts to advance. At some point Littlefinger will try to kill Jon, but will himself be murdered by Sansa.
Finally the big event comes were the Night's King breaks down the wall (or uses Bran's mark, remember that? It broke the wards on the tree, no telling what will happen once he crosses to the other side of the wall. Benjenn showing up a walking, free-thinking undead guy was awfully convenient...), and in doing so he will start taking control of the dead south of the wall. The next part is wishful thinking, but the Night King will take control of The Mountain, since he is basically a Wright himself, and will use him to kill Cersei and detonate the wildfyre caches, but not before Jamie realizes what is happening and evacuates most of the city. Without any options, Jaime meets with Tyrion and is able to surrender. Dany's bittersweet celebration is short lived though, as her forces in the north send her word that they have joined with the northerners (due to Theon) versus the Night's King. She heads north knowing the White Walkers need to be stopped.
How the battle plays out I can't even fathom, so I won't, but I do think with the Night King now in control of The Mountain, he will head north and join his new master in the fight. This will lead to The Hound finally getting his chance to kill his brother, just as he always wanted.