In September, Major League rosters can expand to a maximum of 40 players. This year the Cubs aren’t likely to add many position players to their active roster. However, the Cubs will certainly bring up a ton of pitchers from Triple-A who have already helped the Cubs at the Major League level this season.
However, there are more players who could be potentially get called up than there are spots on the 40-man roster. There are pitchers coming back from injuries. There are prospects the front office might want to have get a taste at the Major League level.