I think the plan is to split it up across more smaller spaces, with more kiosk automation, so as not to cluster everyone waiting in line into one zig-zagged compressed space where a bomber or shooter would have so many sitting targets in easy reach.  Especially with an unsecured railing space in close proximity overlooking the whole area.  Someone could pretty easily walk in with a duffel bag full of guns and  grenades and take out hundreds of people in one fell swoop with the current configuration.

But security is only part of the reason for the reconfiguration.  A design accommodating more automation (kiosks, scanners, etc) should be helpful.  

What I don't buy is the idea that tons of people will be eating and shopping the main hall when it shifts to a security-side space. Once past security, people wanna get to their concourse ASAP. And I don't expect many connecting travelers to go out of their way to the main hall either.