Warning: SPOILERS for Ant-Man and the Wasp are ahead!
Ant-Man isn't always one of the Marvel Cinematic Universe's (literally) biggest characters, but in the last three years, he's definitely become an important one. Scott Lang's origin story unfolded back in 2015, and less than a year later, he aided Steve Rogers and the other anti-Sokovia Accords heroes in Captain America: Civil War. Now Scott is back on the big screen for Ant-Man and the Wasp, where he finally teamed up with a costumed Hope van Dyne out in the field and faced off against the likes of Ghost and Sonny Burch. Marvel's post-2019 film slates shrouded in mystery, so it remains to be seen if a third Ant-Man movie will get the green light. Nevertheless, MCU history, as well as Ant-Man and the Wasp's critical and commercial performance, suggests there's a good chance Ant-Man 3 will happen. Working off that assumption, there's an important question that the threequel needs to answer for audiences: what happened to Mitchell Carson and the stolen Pym Particles?
For those of you who need a refresher, Mitchell Carson is S.H.I.E.L.D.'s former Head of Defense who carried a grudge against Hank Pam dating all the way back to the late 1980s, frustrated that the scientist wouldn't share how to create Pym Particles. Oh, and because Hank slammed his head into a table when he made an insulting comment about Janet van Dyne's death. Decades later, when S.H.I.E.L.D. collapsed due to the events of Captain America: The Winter Soldier, Carson was outed as a longtime member of HYDRA, and after helping "take down governments," he resurfaced in Hank's life when Darren Cross revealed the Yellowjacket suit. Cross accepted Carson's purchase offer for the technology, and Carson showed up later inAnt-Man with some of his HYDRA buddies to make the transaction. Thanks to Scott Lang, Hope van Dyne and the Antourage, the sale didn't go through as planned, and while Cross later died fighting the new Ant-Man, Carson managed to steal the briefcase containing Cross' version of the Pym Particles (getting bitten by some ants in the process) and escape the Pym Technologies building before it exploded.
You'd think that such a plot thread would be addressed in Ant-Man and the Wasp, but not only does Mitchell Carson not show up in the sequel, the stolen Pym Particles aren't mentioned at all. Approximately a year passes between Ant-Man and Captain America: Civil War, and Ant-Man and the Wasp makes it clear that about two years have passed since Scott Lang participated in the Leipzig airport battle, so let's just say it's been three years since the first Ant-Man movie when the sequel begins, just like the wait was in real life. What's Mitchell Carson been doing during this time? Did Scott, Hank Pym and Hope van Dyne make any effort to find him? Are they even aware that Carson stole Cross' Pym particles? There are all these lingering questions, but Ant-Man and the Wasp doesn't come anywhere close to providing any clues. Though part of me wonders if Sonny Burch was working for Carson, and that's who was giving Sonny orders over the phone.
In the grand scheme of things, Mitchell Carson not being addressed in Ant-Man and the Wasp isn't a big deal, as the sequel has more than enough on its plate, from exploring the Quantum Realm to Scott and Hope's rapport in the field to Ghost trying desperately to fix her condition. Both Ant-Man and Wasp are returning next year for Avengers 4, with Scott Lang looking like he'll play a particularly important role (once he's escaped the Quantum Realm, that is), but with everything that beast of a superhero blockbuster has to juggle, the soonest we could get an answer about what happened to Carson is in Ant-Man 3. And make no mistake, we do need an answer about him. For the sake of argument, let's assume that Ant-Man 3 will be the last MCU Ant-Man movie ever. If that's our last opportunity to explore that corner of this world, then Carson needs to be brought back so that story arc can be resolved.
Even with HYDRA being seemingly gone for good (as Agents of S.H.I.E.L.D. has indicated), no doubt Mitchell Carson has plenty of other criminal connections around the world, so it would be easy enough to include him in Ant-Man 3, even though it's unlikely he'd be the main antagonist. Perhaps he's been trying for years to replicate/reverse-engineer Darren Cross' Pym Particles, but has had little luck, echoing his efforts with Hank Pym's creation in the '80s. Maybe the main antagonist, whoever it may be, gets ahold of Darren Cross' research either through a partnership or theft, subsequently using it and whatever technology they have at their disposal for nefarious purposes. Whatever Ant-Man 3's story ends up being, the creative minds behind it would be wise to include Carson in some capacity so we can finally have some resolution with him.