Eh, imo, the only way that a second team comes to Chicago would be to play the Chargers have done in LA - to help pay for the new stadium. I seriously doubt that a new team would want to come in and take over the bad revenue stream situation of Soldier Field - from the team's perspective.
However, I really doubt that the NFL would try to add a 2nd team to Chicago. I would think they would look to add to other markets if they do add teams. I would also add, I hope they do not expand any time soon although I have learned to never underestimate the greed of the billionaire owners.