As we all know, Avengers: Infinity War will see Thanos finally stepping into the limelight and attempting to secure all six of the Infinity Stones so that he can manipulate reality as he sees fit. From what was shown in the first Infinity War trailer, the Mad Titan will for sure obtain the Space Stone and the Power Stone, and one of his minions was shown starting to pry the Mind Stone out of Vision's head. But Thanos isn't the only one who wants all of the Infinity Stones. In Thor: The Dark World's mid-credits scene, Taneleer Tivan, a.k.a. The Collector, expressed that same desire, and with Benicio del Toro set to reprise the eccentric alien, it begs the question of exactly how important he will be to Infinity War's story.
Like the other of his kind, including his brother Grandmaster, The Collector has been around since the universe sparked into existence, and as the centuries passed, he assembled quite the collection of rare objects, artifacts, living beings, etc. The crowning piece of his museum up until recently, however, was the Aether, a.k.a. the Reality Stone, which he received from Lady Sif and Volstagg after Malekith's defeat. But one Infinity Stone wasn't enough for him. So by the time Guardians of the Galaxy began, Collector had hired Gamora to retrieve the Orb, a.k.a. the Power Stone. There was speed bumps along the way, but eventually she delivered the prize with the other future Guardians in tow.
For a few glorious minutes, the Power Stone was in Collector's possession, but when his slave, Carina, attempted to use the purple artifact to escape from his servitude, she was instantly killed, and the museum was destroyed. The Guardians soon took back the Power Stone (only for it to fall into Ronan's hands soon after), and Collector was left sitting in the ruins of his exhibit. Fortunately for him, even with the loss of the Power Stone, he still has the Reality Stone tucked away somewhere. Unfortunately for him, that's going to make him a target.
Which brings us to Avengers: Infinity War, where at some point during the story, we're going to reunite with The Collector. Granted, there's still no guarantee yet that Thanos will successfully obtain all six Infinity Stones, but you can be damn sure that he'll try, and that will mean paying a visit to The Collector. And frankly, we don't like the hoarder's chances of survival. Even though The Collector is long-lived, we haven't seen him display any special powers during his few minutes of screen time. His comic book counterpart boasted such abilities as cosmic energy manipulation, shape-changing, precognition and more, but who knows if the MCU version if capable of doing any of that. Regardless, with his own natural might and presumably the Space and Power Stones already in the Infinity Gauntlet, Thanos has the advantage. We don't even know if Collector is capable of manipulating the Reality Stone on his own. So whenever Thanos and The Collector cross paths, it's almost certain that the former will take the Infinity Stone away from the latter with ease.
However, there is a chance that The Collector could make it out of Avengers: Infinity War alive. While Collector is a being whose only allegiance is to himself, he may decide to somehow aid the Avengers, Guardians of the Galaxy and other MCU heroes in defeating Thanos if it means he's once again close to obtaining the Infinity Stones his collection. So if something or someone interferes with Thanos killing Collector, it's possible that he may throw his hat into the proverbial ring, and his role could continue into Avengers 4. Marvel Studios president Kevin Feige has also expressed interest in one day pairing Collector and Grandmaster together in a movie, so perhaps that bodes well for his future.
But once again, we have to remember how mighty and ruthless Thanos is. It's doubtful he would leave someone like Collector alive even after stealing his most valued treasure. If that's the case, then The Collector's role would be minor at best. While Collector would be more valuable to the protagonists alive then dead, we also wouldn't shed too many tears (if any at all) for his demise, as not only is he a cruel figure who locked up living beings simply to display them in his museum, but like Thanos, we doubt he would be a benevolent god with the Infinity Stones.