MacBook 2016 13" case warping

Like a few others, I've noticed that my MacBook Pro 13" (2016, with strip) has a warping case bottom. It appears to be swollen in the middle. It's had this problem for at least a year, and it doesn't appear to be getting worse.

Coincidentally, the track pad appears to need a little more of a push to select an item. Otherwise it appears to be functioning normally.

I've seen only two answers, both talking about swollen batteries. Could there be another reason, perhaps overheating over time?

Is my best option to bring it to the Genius Bar at our nearest Apple Store? If I do, how much does a case replacement cost (approximately) and how long does it take to do?

Many thanks.