The Twilight Eclipse ending settles three things at once: the newborn army is destroyed, Victoria is dead and Bella has chosen Edward over Jacob. In my opinion, the film earns that last point better than many love triangle stories, because Bella says it plainly after the tent scene and again once Jacob recovers.
That tent scene is the hinge. Bella kisses Jacob during the freezing night in the mountains, and it is easy to read as a wobble. I read it the opposite way: she tests the feeling and comes away more sure that her love for Edward is the stronger one. Compare that with the first film, twilight 2008, where the question is whether Edward is dangerous, and with twilight new moon, where Bella is left alone after the Cullens leave Forks. Eclipse is the first film in which she is the one making the decision.
The Volturi arrival deserves the most attention. Bree Tanner has given up, and Jane has her killed anyway. Jane was already feared in New Moon, and here she shows the Volturi enforcing rules without any argument, a cold reminder that the Cullens are being watched. It points toward the larger conflict that returns when Irina misreads Renesmee in breaking dawn part 2.
The alliance matters as much as the romance. Jasper teaches the Cullens and the wolves how newborns fight, drawing on his own past, and that training turns old enemies into one fighting unit. Edward killing Victoria and Riley closes the revenge plot that Victoria carried from earlier films, which is why the battle feels like a finish rather than a pause.
Jacob's acceptance is painful rather than tidy. He is badly hurt in the fight, he recovers, and he hears her decision. Perhaps that is why the final scenes feel quieter than the battle: the wolves and the Cullens fought side by side, yet the personal cost lands afterward.
The closing beat looks forward, as Bella and Edward get ready to tell her father about their engagement and the story points toward her change into a vampire. It could be argued that Eclipse is where the saga stops asking whether she will choose and starts asking what the choice will cost.