Ant-Man & the Wasp: Quantumania is the third film in the Ant-Man franchise. There are some lingering questions that have not been answered from prior films as well as the MCU as a whole.
Who did Sonny Burch work for?

Sonny Burch played by Walton Goggins was an antagonist in Ant-Man and the Wasp. He was after the Mobile Laboratory so he could sell the Quantum tunnel. It was revealed that it was for his employer, but it was never answered who sent him. This is a lingering question that fans would like an answer to. Sonny Burch has not appeared in a Marvel film since. I highly doubt he will be in Quantumania but I guess anything is possible. You don’t necessarily need Burch in order to answer who his employer was. It can be answered in a simple line of dialogue. It could be something as “Sonny Burch from a few years back worked for…” as an example or “…that’s the guy who hired Burch.” The employer could be nobody but given its Marvel, a lot of fans viewed it as the employer is somebody important. One popular theory has been that Norman Osborn is the employer. Currently its not known where an MCU Norman Osborn stands. In Spider-Man: No Way Home, it was stated by William Dafoe’s Norman Osborn that there wasn’t a Norman Osborn in this world. That could also be a misdirect or that he simply didn’t know there was one. Even without Burch being in Quantumania it is possible to still answer who his employer was especially if the employer has a fascination with the Quantum realm. I also have a feeling that this probably will be a lingering question for a little while longer.
Who was Agent Jimmy Woo’s informant?

Randall Park reprised his role as Agent Jimmy Woo in Wandavision. It was revealed that he had someone on the inside in Westview which was sealed off because of Wanda Maximoff. By the time the series ended it was never answered who the informant was, or what they were an informant for. After the show, it was stated that this would be answered later on. Here is the best opportunity to answer that since Jimmy Woo is in the movie. Currently beyond Quantumania it is not known when Agent Woo will show up again. This would be the best time to answer that lingering question. I think there is a good chance we could get an answer since Woo is in the movie, unless he is trapped in the Quantum realm, I would think he will probably have the only scenes in the regular world. Based on the marketing it is obvious most of the film is going to be in the Quantum realm focusing on Scott Lang, Hope Van Dyne, Hank Pym, Janet Van Dyne, Cassie Lang, and Kang the Conqueror. If Jimmy Woo has a semi decent sized role it most likely would be him working on a case in the regular world. I don’t see him getting trapped in the Quantum Realm, but anything is possible especially after the events of Wandavision.
Is Darren Cross alive?

Darren Cross played by Cory Stoll was the villain in the first Ant-Man. He was Yellowjacket and during the climactic battle with Scott, Yellowjacket was shrunken down to the atomic level and was presumed dead. Since the first movie, fans never really believed Yellowjacket was dead. There was always a question if Yellowjacket would return in Ant-Man 3. There is a new question. It has been revealed that Cory Stoll will be playing MODOK in Quantumania. Now, fan theory is that Darren Cross has become MODOK. If that is true, I feel it will be answered in the movie especially since this will be the first time meeting MODOK. I think either way it will be answered. It could be a case that Cory Stoll just landed another Marvel role. Gemma Chan and Michelle Yeoh played two different characters in the MCU. It is not completely out of the realm of possibility. There is also the chance there could be a twist and that while down in the Quantum realm, Scott and Hope and Cassie could run into Darren Cross which would reveal he is alive. A further twist could be if MODOK is after Cross for some reason.
Are Shang-Chi and Ms. Marvel connected to Quantumania?

As seen in the photo above, fans have picked up on similarities between these objects. The bottom is from the Quantumania trailer which has a striking resemblance to Ms. Marvel’s bangles and the weapons that the Ten Rings used in Shang-Chi. The top left corner photo is from the season finale of Loki. It is on He Who Remains’ desk. The design is similar to the other objects in the photos. Will this get answered? I think one way or another this will get answered.
Will the Loki Season Finale be acknowledged?

This is a big question, for me anyway. In the season finale of Loki, Loki and Sylvie opened the multiverse when Sylvie killed He Who Remains played by Jonathon Majors. He Who Remains is supposed to be a variant of Kang. Once He Who Remains was killed, it essentially freed Kang and will probably be a key factor in the plot of the Multiverse Saga. The show already stated there was a multiversal war once before. I think it is safe to presume that by the end of Quantumania, Kang will be free, and he will be unleashed in the MCU therefore endangering the entire Multiverse. My main question is when this happens will this be at the same time as when Sylvie kills, He Who Remains? Will this get answered in the movie? I hope so. What are the chances it will? Your guess is as good as mine. It could be subtly answered or answered off screen from Marvel Studios directly.
Will Quantumania connect all of Phase 4?

Kang knows about the Multiverse. Kang is probably aware of all of the events in all timelines including the MCU timeline. That would mean he knows events that transpired in Eternals, Shang-Chi, Spider-Man, Wandavision, etc. Will this be the movie to prove once and for all that Phase 4 is still connected to the bigger picture? That has been a common complaint by fans. I think the chance this will get answered is very likely.