While Game of Thrones didn't specifically adapt the valonqar prophecy into the show's canon, it's looking more and more likely that's the way things will play out. A throwaway line from Tyrion in season 8, episode 2 and some depressing military statistics delivered by Jaime feel like the foreshadowing of another round of Lannister kinslaying.
The Game of Thrones season 5 premiere, " The Wars to Come," opens with the series' first (and only, if you don't count Bran's visions) flashback. In it, an arrogant, teenage Cersei visits a witch on Lannister lands and demands a fortune. She gets far more than she bargained for when the witch accurately predicts that Cersei will have three children each of whom will die. Something similar happened in A Feast for Crows, Book 4 of A Song of Ice and Fire, with Cersei remembering the interaction; but, in this case, the witch tells the future queen that not only will she bury her children, she'll also die by the hands of the valonqar, High Valyrian for "little brother."
Because Game of Thrones noticeably chose to exclude this portion of the prophecy when adapting the sequence, there's been a significant amount of speculation regarding whether or not Cersei would, in fact, die at the hands of one of her brothers (strangulation, to be specific). But "A Knight of the Seven Kingdoms" included some elements that imply they're still moving in that direction.
When Tyrion and Jaime walk the battlements of Winterfell, Tyrion remarks that "At least Cersei won't get to murder me. I'm sure I'll feel some satisfaction denying her that pleasure, while I'm being ripped apart by dead men. Maybe after I'm dead, I'll march down to King's Landing and rip her apart." It's a jape typical of Tyrion, but given what we know about the valonqar prophecy and Tyrion and Cersei's mutual distaste for each other, it's a pretty pointed joke for Cersei's littlest brother to make. It's unlikely the conclusion of Game of Thrones includes an undead Tyrion choking his sister to death, but it would be satisfying on several levels if he were instrumental in the death of the sister who'd tried to murder him several times over.
But beyond Tyrion aimlessly musing about it, Cersei's murder - regardless of who commits it - is starting to look like the only option left when it comes to defeating her. Jaime not only brought news of her treachery to Winterfell but also her acquisition of the Golden Company and its 20,000 troops (more than enough to defeat the survivors of the Night King's onslaught). Negotiating with the Mad Queen clearly doesn't work, and odds are, Euron Greyjoy would be just as intractable. And since it's unlikely Dany and company will be able to defeat her in battle (the dragons haven't emerged as the superweapons they were alleged to be), the only solution might be an assassination.
That said, now's a good time to point out that Jaime Lannister is the younger of the Lannister twins having been born just after Cersei famously emerging from the womb grasping her ankle. Technically "little brother" could also refer to him, and Jaime could certainly be forgiven for wanting his twin dead. But that would prove a pretty dark and tragic end for a character whose redemption arc was so beautifully wrought.
It's still far too early to call whether or not Cersei will die at the hands of one of her brothers, and to be honest, there are other characters (Arya, Gendry and Sansa would all fit) who would also make for satisfying ends to Cersei's reign. But considering what a prominent position the valonqar prophecy occupies in the overall mythos of Game of Thrones, it remains a very tempting subject for speculation and would make for a pretty resonant end to her story.