Yog, good topic. Because of the show being chronologically ahead (or even completely different) from the books, you might want to clarify the spoiler alert to something like Massive HBO show SPOILER ALERT! Seriously people, when I say Massive, I mean Red Wedding level SPOILER ALERT!
I will make a few comments upon HBO's plot endings... Caveat Reader.
Dany, Selyse, Cersei, and Margaery are the Queens and Dowager Queens at the moment. Asha, Arianne, Sansa, and Shireen seem to be the most likely to be added to the list in the near future. Remember Maggy the Frog's prophecy to Cersei? She claimed Cersei's children would all wear crowns and would all preceed her in death... being shrouded in gold. I believe that Myrcella will certainly be a queen and will certainly die.
I predict that Dany lives at least until the last four chapters of ADOS... and probably will survive the story. Cersei will not die in TWOW, but in the last half of ADOS... at the hands of the Valonqar. (My candidates for Valonqar include Jaime and Tyrion, natch, but also Dany and Jon.) Selyse will die either at the hands of Wildlings or Undead... sooner rather than later. I refuse to believe GRRM's end for Margaery until I see it in print.
Arianne will die in the game, she's too short sighted to survive the game. Asha cannot survive the blizzard, Stannis, Ramsay, Euron and the oncoming Winter. Shireen will most likely perish alongside Selyse. Myrcella will die at the hands of Cersei's enemies... Dornish, Targaryen loyalists, the Golden Company, etc.
Sansa is the only one who I believe will survive. Forget HBO's story for Sansa. She's with Middlefinger. She is a Stark. She is the Stark bloodline... not Jon, not Robb's child, not Arya, not Rickon and definitely not Bran. She is the redemption, the continuation, and the victory for House Stark. She won't be unscathed, but I think she'll be one of the three heads... Dany's surrogate baby mamma or Faegon's bride.
But Boaz, who are the actual Queenslayers?
Wights will kill Selyse and Shireen... and Asha.
Sand snakes or some other Dornish faction will kill Arianne... perhaps even the guy Doran is sending as her bodyguard.
Qyburn will torture Margaery to death.
And Cersei? And Mycella?
Well, everything we know about Maggy's prophecy seems to be coming true. Melara Hetherspoon died the very night of the prophecy. Cersei married the King. She had three children and the King had sixteen. (I don't know if the story has shown all sixteen of Robert's bastards, but I don't doubt Maggy on this point.) Joffrey was a king and is dead. Tommen is now King. Myrcella is betrothed to Tristayne Martell, now second in line to the Dornish Throne. (But let us not forget that Myrcella was already called Queen by Arianne and her conspirators. She may have never technically been proclaimed and crowned, but an attempt was begun on her behalf.)
Which brings me to the two parts of the prophecy not yet covered...
First is the younger more beautiful queen who will supplant Cersei. I do not believe this is Myrcella. She'd never challenge Cersei... and because of the use of valonqar later in the prophecy, I suspect Maggy would have used a more familiar term than queen... i.e. daughter for Myrcella, daughter in-law for Margaery, sister in-law for Sansa. In my opinion, only Dany (mayhaps Sansa) could be considered more beautiful than Cersei. The prophecy says something like, "... until a younger and more beautiful queen comes to take all you hold dear..." All that Cersei holds dear is her children and power. Since Dany is this younger queen, I believe that one of Dany's dragons will eat Myrcella. They may eat Tommen too.
But Boaz, if Tommen is King, how will Myrcella ever be Queen?
Easy. I believe that Aerys II, the Mad King is Cersei's father. This explains Cersei's incest and growing mental instability. If she defeats the Martells, the Sparrows, the High Septon, Grand Maester Pycelle, and her creditors in one fell swoop (as HBO would have us believe), then she'll be unopposed in power and she'll have done what not even the Mad King could do... and she'll lose most of her grip on reality. At this point, if she can get Myrcella back, she'll marry Myrcella to Tommen as she wanted to wed Jaime. Thus, Dany can feed Tommen and Myrcella to her dragons.
The second part is that the valonqar will choke Cersei to death. In my mind, Aerys II, the Mad King, had seven children. Three by his wife Rhaella... Rhaegar, Viserys, and Danaerys. Three by his secret lover/rape victim #1, Joanna Lannister... Cersei, Jaime and Tyrion. One by rape victim #2, Lyanna Stark... Jon Snow.
Cersei translated valonqar from Valyrian to Westerosi as "younger brother." But remember that Maester Aemon always translated "the Prince that was promised" from Valyrian to Westerosi incorrectly. At the end of his life, Aemon remembered that Prince in Valyrian is gender neutral... so the translation "the Princess that was promised" is equally valid, and moreso since Rhaegar and Viserys were dead, but Dany was alive. I believe that Cersei (not even one hundredth the scholar that Aemon was) has misinterpreted valonqar. Instead of "younger brother", I think it should be translated as "younger sibling." Then according to birth order, Cersei's younger siblings are Jaime, Tyrion, Viserys (deceased), Jon, and Dany.
Bearing in mind the mention of golden crowns and golden shrouds in the prophecy, I'd expect Jaime's golden hand to be mentioned if he is Cersei's killer. And when it comes crashing down... will Jaime have it in his heart to kill Cersei? I think not. Unless it's a murder suicide, "If I can't have her then no one will. We'll go out together." I used to think GRRM was going to do this for Jorah and Lynesse Mormont, after Dany banished him.
Tyrion has choked a woman to death before... and he'll arrive with Dany as a member of her Small Council. Tyrion is a likely candidtate for valonqar. The strongest case against Tyrion is that this is already what Cersei believes. Her political acumen is usually wrong... as is her understanding of Maggy's prophecy. Since Cersei thinks it will be Tyrion, it probably won't be Tyrion.
Jon. Cersei's already plotted to kill him. She schemed for the downfall of Eddard... and Jon blames her for Eddard's death. He most likely blames her for Robb's as well. If he ends up on the Iron Throne with Dany, he seems a likely candidate to choke the life from Cersei. But I think the climax of his story is in the battle with Winter... with The Other. It won't do to have him win both the supernatural and the political battles.
Dany is the valonqar. She will kill Cersei. She is the younger, more beautiful queen. (Yes, I know I argued about the use of more familiar language earlier, but Myrcella, Margaery, and Sansa are people close to Cersei. She knows them. Dany, even as Cersei's sister, is a stranger to her.)
