if I'm not mistaken, those are your 2 CPU drawers, so you can upgrade to 16 way, but it means shutdown, taking the two-drawer system flex-cables off, adding extra CPU drawer(s) and connecting all with 3-drawer or 4-drawer flexcables.
Might also mean repositioning the existing drawers to higher EIA-slot-numbers because additional CFPU drawers are added downwards from your first CPU drawer in the rack. You may also need additional PDUs in the rack...
HTH,
p5wizard