Once again, Ant-Man is going to be given an ultimatum in another one of his titular titled movies, when he will be thrust into the grand plan of Kang The Conqueror; either use his heist skills to get Kang what he needs, or the existence of life as he knows it will crumble.
Quite the burden to bear.
After watching the new 'Ant-Man and The Wasp: Quantamania' trailer repeatedly, a new theory was born, and I believe that this theory is what will lead to the beginning of 'Avengers: Kang Dynasty.'
As far as the general story goes, we know that in order to save the lives of his friends and daughter, Scott will be instructed by Kang to return a stolen item for him. I believe this specific "item" to be Kang's "Time Chair"; it is what he uses whenever he wishes to travel throughout time.
The more Kang does not have the Time Chair, the more trapped he will remain in the Quantum Realm; it is extremely essential to Kang, so keep that in mind.
Recently, the runtime for 'Quantamania' had been revealed to be as long as a little over two hours. If what we know about the logic of the Quantum Realm, is that an hour in there, can be equivalent to a year in the outside world, then Scott and his friends are going to miss quite some time.
The timetable works like this: Scott and his friends get sucked into the Quantum Realm in the current day MCU timeline; Kang keeps them trapped there for a couple of hours according to the movie's actual runtime until Scott steals Kang's Time Chair for him; meaning that a couple of years will pass by the time the movie ends.
In the real world, Scott and his friends are nowhere to be seen, and as the normal MCU timeline continues, there can be subtle hints of Ant-Man's disappearance like "yeah, Ant-Man has not been seen in a while."
Once Scott and his friends are free to go at the end of 'Quantamania' they come back to the future year when 'Avengers: Kang Dynasty' will take place. 'Quantamania' had been confirmed to have the same impact that 'Civil War' had on 'Infinity War', it can essentially work as the prelude, and beginning of 'The Kang Dynasty'.
Kang has been freed from the Quantum Realm and is ready to wreak havoc on the world.