He proposes that Dany will be sentenced to death after the burning of the Red Keep by Cersei. Now, this could be tough after what we saw looked like Cersei's demise. But either she didn't actually die, or there are other characters around that could see this part of the hypothetical plot through.
Caldwell goes on to write this about Dany's death sentence, following her being assaulted with that green wildfire:
"Then, in a growing and brilliant green firestorm, born… Daenerys, the Targaryen her ancestors dreamed of, that her father envisioned being, will be "reborn as a dragon to turn enemies to ash." The Daughter of Death, true to name. Breaking the chains of her human form, her chrysalis, she'll spread her wings and transform into the Largest. Dragon. Ever. Seen. No weapons, no armies, will stand a chance against her. She'll demolish everything in her path. Burn the entire city. Madness. End times. Pure Fire and Blood." She will burn King's Landing and its men, Cersei and even the throne room. Her vision from the House of Undying will finally come true. It wasn't snow that we saw but ashes, that she herself was responsible for.
I mean, please let something like this happen. It'd line up with that viral Game of Thrones theory from last week that suggested we haven't seen all of the show's dragons yet; and it'd do it in the kind of epic, jaw-dropping, electrifying way that would send the audience into tears of overwhelmed amazement.