There are two fleets on their way: the Iron Fleet (Victarion) and after them the Volantine fleet. The Iron fleet are almost there, and will likely arrive before Dany returns. The Volantine fleet started out later and we do not know how the storm affected them. FWIW, I will guess that Victarion's arrival will lead to Ser Barristan putting the plan he and the council agreed into effect---after he gets thru' asking himself "what in the seven hells are THEY doing here?", and observes them attacking the ships of the blockade. What the Second Sons and Windblown will do is also up in the air. Still the arrival of the Ironmen should be enough to turn the day. After that who knows? (Other than GRRM.) Maybe they move the Iron Fleet up the river, hunker down and await a second siege. Maybe that gives Dany enough time to impress the Dosh Khaleen with Drogon, have them order enough Dothraki warriors to follow her, return to Meereen, break the second siege, and then---finally---capture enough ships and supplies to carry her and the unsullied and freedmen, second sons, and windblown to Dragonstone via Volantis and Pentos. (Where Khal Pono figures in this I dunno. What happens to Victarion and the dragon horn, also I dunno---except that (1) Dany will be furious if she thinks that he is trying to steal HER dragons and (2) Moqorro will act ruthlessly to try to stop Victarion from getting in the way of the fulfillment of the prophecy.
Edited by Old-Growth, 10 December 2012 - 12:53 AM.