As much as I love the current 3.8 even with the reduction to only 311 hp I believe it should be replaced with the new 3.3 TTV6 for the Genesis G80.
Looking at the current segment, as well as near FUTURE engines, the midsize lineup for mid-range engines will be:
Next gen Audi A6: Engine shared with 2017 S4 3.0 Turbocharged V6 354 hp 369 lb-ft
Next gen BMW 5-Series (540i): Engine shared with new 340i 3.0 Turbo I6 320 hp 340 lb-ft
Mid-Refresh
Cadillac CTS: 3.6 V6 335 hp 285 lb-ft
Genesis G80 3.3 TT V6 365 hp 379 lb-ft
Jaguar XF 35t/XF-S: 3.0 Supercharged V6 340 hp 332 lb-ft/380 hp 332 lb-ft
Maserati Ghibli/Gihibli S: 3.0 TT V6 345 hp 369 lb-ft/404 hp 406 lb-ft
Mercedes Benz E400/E43 AMG(yes this is real): 3.0 TT V6 329 hp 354 lb-ft/362 hp 384 lb-ft
This engine will be in the upper midpack but it is a much needed engine given the G80's heft.
Also this can't replace the 5.0 V8 unless they upped the power to the loww 400 hp range.