renovation should be wrapping up soon. They've been closing off sections of each building and renovating them for the past few years. That would explain the "abandoned" areas.
I was at MCI
back in November, and they were remodeling the last section of each terminal. I have to think they'd be almost done by now, if they aren't done already. My Southwest flight arrived into one of the "old" sections - the wooden floors were worn down to floorboards. The remodeled sections were definitely much fresher looking.