Although Avengers: Infinity War strongly suggested The Collector's death during Thanos’s assault on Knowhere, as he was depicted as being tortured by the Mad Titan before his collection was obliterated, it was later confirmed that he survived the attack. The scene turned out to just be an illusion, and James Gunn later confirmed that The Collector survived Thanos' attack.
So the door is definitely open for the character's return.
While out promoting the release of his new film, The Phoenician Scheme, Benicio del Toro stated that it's up to Kevin Feige and co. on when and if he returns, but he's game if he gets the call. “I don’t know. I mean, it’s like, you gotta get invited to play in that international tournament, and I’d love to play in it, but fingers crossed that’ll happen soon,” he said. “I haven’t been invited yet for a second round.”
With a multitude of familiar faces slated to reappear in the monumental Avengers: Doomsday and Secret Wars, it raises the question of why not Benicio del Toro's Collector?
In the Marvel Cinematic Universe, Taneleer Tivan, as depicted, is a stark contrast to his comic book counterpart. In the source material, The Collector is a formidable member of the Elders of the Universe, an ancient group of beings, which also includes The Grandmaster (played by Jeff Goldblum in Thor: Ragnarok).
These cosmic entities are not only immortal but possess the incredible ability to manipulate cosmic energy, yielding a vast array of powers. The MCU's adaptation of these characters, however, has largely portrayed them as merely incredibly old and eccentric, seemingly devoid of their comic book abilities.
Despite this significant power downgrade, the opportunity to reinvent The Collector, should the story demand it, is absolutely present.
As demonstrated in What If...? Season 1, Episode 2, "What If... T'Challa Became a Star-Lord?", The Collector's true strength can lie not in inherent cosmic powers, but in his vast, dangerous collection of artifacts and weaponry. In that alternate reality, by cleverly combining the formidable gadgets and items he had amassed, The Collector transformed into a surprisingly potent powerhouse, capable of holding his own against the team-up of T'Challa/Star-Lord and a reformed Thanos.
Just for fun, imagine a reimagined Multiverse Saga where instead of Kang, the spotlight falls on Benicio del Toro’s Collector and Jeff Goldblum’s Grandmaster. What if these eccentric cosmic beings united to form the Elders of the Universe, launching a reality-spanning vendetta against Earth’s Mightiest Heroes for past humiliations?
It's a wild "what if," but one that has the potential to deliver something more visually dazzling and delightfully offbeat than what's been delivered to date.