night's episode. first, I think Varys was successful in sending out several of those letters before he was captured. He had written roughly 5-6 when the girl came to visit during the day and only burned the last one when he was captured later that night. presumably the others were already sent by raven. There is a prophecy in the books not spoken on the show so maybe a stretch to think D&D are even aware of it but here it is...

In the books Dany was also warned by Quaithe - the weird character in Qarth - with the following, “The glass candles are burning. Soon comes the pale mare, and after her the others. Kraken and dark flame, lion and griffin, the sun's son and the mummer's dragon. Trust none of them. Remember the Undying. Beware the perfumed seneschal."

Obviously Arya is on the pale mare. The Kraken is sigil of the Greyjoys (Yara now commanding), the lion would be Lannister with Tyrion being the only one of note now, the sun is sigil of house martell but they are virtually all gone on the show, the mummers dragon would be Jon Snow (really Aegon Targaryen) - according to the books, the Griffin belongs to house Connington which existed prior to an up to Roberts Rebellion but they have never been mentioned on the show, so likely not involved and really not sure about the dark flame but there is a character named Moqorro in the books who is another red priest that could be considered the dark flame. One episode left and this prophecy was never on the show so maybe none of this happens - but I have to imagine multiple houses rebel against Dany with the leadership of the Starks - very similar to Robert's Rebellion

So Varys successfully notifies all of these people and they come to aide Jon & the Starks in another rebellion. Maybe Bran can assist with the dragon but not sure. It may also take something significant, like Arya being caught and killed, in order for Jon to finally come around and lead the charge. If he doesn't die, my guess is he walks away from the throne and ends up north of the wall with the free folk & his wolf and someone else, or some combination of folks, put Westeros back together and lead in some more democratic way