Daenerys Targaryen has suffered many losses during the short but intense seventh season of Game of Thrones. In the span of mere episodes, she has lost her best allies — the Martells, the Greyjoys, and Olenna Tyrell — as well as one of her dragons, Viserion. Thinking about Viserion's death and subsequent resurrection as an Ice Dragon while looking ahead to the future, it's not unreasonable to think that Daenerys' dragons will die in the Season 7 finale. In fact, considering Season 7 has been actively focused on setting Daenerys back, it's almost certain her dragons, Drogon and Rhaegal, will die.
Despite the fact that Season 7 has proven kind to Daenerys when it comes to developing her romance with Jon Snow, the plot of this season has been unkind to Daenerys in terms of advancing her closer to the Iron Throne. Despite it being her true and sole dream to take the crown, she has suffered crippling losses. This emotional weight is compounded when we consider that we have been reminded a number of times that Daenerys is both infertile and that she considers her dragons to be her children. In understanding that relationship with her dragons, it's almost as if GoT is signaling to us that she will in fact suffer the loss of both Drogon and Rhaegal (in a Chekhov's gun kind of situation) because it's been impressed upon us that she suffers any pain done to her dragon children on a very real level.
As the stakes get higher for Daenerys, with dwindling troops and the reveal of ace card (her dragons) to the Lannisters, she is now prone to making mistakes. A thirst for power means Daenerys will inevitably mess up and make a bad decision as she fights her way to the Iron Throne. It is very likely she will make a bad decision when it comes to how she uses Drogon and Rhaegal in battle and she could end up putting them in harm's way without thinking ahead about it.
There's also the very real chance that Viserion, now an Ice Dragon, will be guided by the Night King to kill his dragon brothers. As sad as it will be to see Viserion turn against his brothers, he is one of the only real threats against them as a dragon that breathes ice rather than fire. Again, it would be a huge blow to Daenerys and right now, it's a very real possibility.
A lot can happen during the GoT Season 7 finale and that includes the deaths of Daenerys dragons. It will be a huge blow to our Mother of Dragons is she does lose her children, but it could also be a harbinger of the kind of fire and fury she will bring to the war against Cersei in Season 8. Let's hope she doesn't lose Drogon and Rhaegal, if only for Cersei's sake.