This applies to just about every stadium in the NFL right now (except maybe FedEx LOL) but they're going to build new ones in Nashville and Buffalo and Chicago is thinking about moving out to the suburbs.
Buffalo I can understand, but the Titans stadium opened in the late '90s and Soldier Field II is barely more than 20 years old. Taxpayers ought to be furious.
Here's an interesting article on what's going on around the league. It's nearly a year old, so some facts may have changed. It seems Baltimore, Jacksonville, and Carolina are considering significant renovations, too.