So They're Just Gonna Reverse Time, Right?
In some form or another.
Dr. Strange said that he would happily let Stark die than give up the stone. Then later, he completely changed his mind having seen the many potential outcomes (only one of which they win).
It would suggest Stark is integral to that win. Ant-Man being in the quantum realm may also be important.
But it seems clear that they will ultimately reverse time, right?