If you look at the big four, the mergers usually resulted in either a brand new ops center or a renovated one. I would imagine similar for this F9/NK merger.
L-AA had just finished an SOC refurbishment/renovation project when the L-US merger was announced. L-US was also in a relatively new OCC building in PIT. When both combined, a new building was built. SWA built its current NOC right around the time they merged with AirTran. UAL moved into new NOC at Willis after the CAL merger.
Things to look out for over the next few years if merger passes regulatory hurdles: Mergers typically result in some kind of attrition from people not wanting/able to move. Growth in dispatch headcount is possible depending on how workload/systems are integrated. JCBAs from mergers have so far normally resulted in significant gains in compensation for dispatch groups. The big JCBA question right now is does the joint group go with PAFCA or TWU?