Actually, the rebound has started. Ever since Moncada was called up, attendance has been creeping back up. Now, as more of the future cogs are added to the MLB Roster, you will see that continue to move up.
10 years from now, The Cubs will be here on the list. The changes that they have made to Wrigley and the surrounding area have erased the nostalgia reasons to visit the part. They are also erasing their "Fan Farm System", as the buildup of Wrigleyville is pushing out the affordable apartments that young, just out of college students used to flock too. Many of these people were actually from all over the Midwest and further and moved to Chicago for jobs and sometimes along with college friends. Living in Wrigley, they naturally became Cubs fans over time. Now that they will not be in that vicinity is such numbers, the fan base will erode.
"Always look on the bright side of life!"
Eric Idle