Its certainly possible. We know there is a greater House Martell plot. But we don't know what it is in the show or the book so its really up in the air. I am guessing that Ellaria will be brought into the fold on it next season, rather we will be shown this, and hear more of Doran's plot.
But killing Myrcella doesn't really do anything for them that I can see. Last thing that Doran did in the books was ready Dorne's Army for the next part of his plan. Whatever the fuck it was, had something to do with attacking while fAegon's Golden Company was attacking. But that may have just been to take advantage of two separate fronts. Book Doran, and show Oberyn really didn't care for anything other than revenge against the Lannisters. But doing so in a way where everyone knew it was them but couldn't retaliate in any way would complete the circle and be poetic.
Unless they're banking on King's Landing not being able to retaliate against Trystane. Which would make sense, as Dorne was able to do nothing against the Lannisters for Elia Martell and her children all the while knowing they were responsible. But this entire theory relies on them somehow knowing that Kevan is in charge and not batshit Cersei. Although I suppose Trystane would not be brought into the plot so his grief was real and then Cersei would be in the position of knowing Dorne had done it but being unable to do anything about it and Trystane's position would be more cemented.
IDK, just a thought.
Actually we know exactly what Doran's "greater House Martell plot" is, and it's equally as stupid as killing myrcella right after putting his son on a boat with jaime and bronn. There is nothing about his plot that is "up in the air" it's just a retarded because he is retarded. or more likely grrm got tired and just phoned it in.
1. Send autistic son to Dany with letter in hand re: Viserys & Arianne arranged marriage and hope she honors the spirit of the arrangement.
2. Send sand snakes/arianne to infiltrate KL.
3. Wait for austistic son to woo dany and have her bring her dragons and army to invade westeros
4. ???
5. Profit
Little does he know that his "master" plan has already failed and his daughter, even after being brought in on the secret, is already calling an audible and hot routing to Faegon's camp.
Doran's grand scheme is only slightly less retarded than Arianne's initial plot to Crown myrcella to rally Dorne to declare war, because she confuses sparsely populated easily defensible desert with military strategy and thinks the smallest and weakest of the 7 kingdoms can some how siege KL. Cersei is certainly not going to invade dorne to murder her own daughter even if her plan had worked and all of dorne declared Myrcella queen of the 7 kingdoms. Oh look, only dorne agrees, so really it makes Myrcella Queen of Dorne. the moment she marries Trystane she becomes Princess of Dorne anyway, so literally nothing happens, other than Dorne loses their seat on the small council and any say in the running of the 7 kingdoms until they stop calling her queen.
I never said that I thought Doran being "in" on the killing was a smart plan or made sense, only that my initial reaction to the way the TV series showed it made me think that. It's entirely possible that they are making TV Doran as retarded as Book Doran. But you guys are right it's probably more likely that Ellaria was just being a cunt.
