Cub fans are the only people who are fixated on attendance figures at Sox games. They dream of the possibility of the Sox leaving Chicago, but that is never going to happen. First of all, the Sox have been in Chicago longer than the Cubs. Secondly, the league would never allow it. Third, Reinsdorf's sons have never indicated they would ever be interested in selling. Cub fans keep repeating a comment JR made to the effect that if his sons sold any team, it would be the baseball team but that doesn't mean they would even want to and if they did, chances are it would be to someone like bill Wirtz or a group of Chicago based investors, including those who already have a stake in the team.
It is inevitable that the lakefront will be developed from McCormick Place South. That has been discussed since the Burnham Plan and brought up numerous times over the years including when the City was bidding for the Olympics. The City is now discussing bringing the Lucas Museum here (although Rauner opposes what appears to me to be a very sensible plan to locate it where McCormick Place East is).
Eventually, that is going to happen. As part of that there there will likely be a new stadium. The White Sox are the logical tenant along with either the Bears or another NFL franchise ( perhaps a successor to the NFL's Chicago Cardinals) for a stadium right on the Lake. Until then, neither the White Sox nor US Cellular are going to go anywhere.