Marada78

I think that the showrunners are going for this "implementation" of the Azor Ahai profecy: Jon is Azor Ahai, Dany Nissa Nissa, Drogon is lightbringer. Dany will get pregnant hence will not be able to ride Drogon any more. At that time both Viserion and Rhaegal will be goners. Also at a certain point they will find that the NK is immune to both obsidian and valyrian steel and dragon breath might be the only way to kill him. So Jon will try and succeed in riding Drogon. Dany will also die of childbirth to completely fulfill her destiny as Nissa Nissa. Jon then will kill the NK using Drogon in a sort of "Kamikaze" action which will be pretty much the end of all three.

All this Season is fan service. GRRM gave them the point of arrival and they decided to get there by fanfic. About this episode is 6/10 because I am rating the level of fan service and with Gendry return and Jon petting Drogon it was ok.

They are becoming separate not only in media or details but in the main storyline also. Soon they will be completely different stories considering that they are probably already scripting season 7 and TWOW is nowhere near to publication. And PROBABLY the show finale will influence GRRM when writing the last book. That is IF the last book will ever come into light.