Changing to 50 Hz would be very hard unless there was a 16.7% voltage reduction (although going from 480 to 400 is that percentage). That kind of voltage reduction would mean more current and more wiring losses. Or all those transformers have to be changed out. Keeping 60 Hz would be fine. Keeping the voltages we already have would be fine. Adding to it would be desired.
We already have 240 V in homes. We just need to learn to use it, which includes tweaking NEC 210.6 a bit. We can run fluorescent lighting on the existing 240 V if we use double pole switches. Computers, and an increasing number of other electronics, will run fine on 240 V. There are NEMA-6-15P to IEC power cords available.
Making 400/230 or 416/240 (at 60 Hz) available on request, where 480/277 would be available, and making 240/480 available on request, where 120/240 would be available, would help. Allowing 2 different systems at the same time in electrical service (avoids the extra transformer losses where both 120/208 and a higher voltage at the same time, are desired) would help. They just need to bring it all in on a combined neutral to avoid the dual path issue across ground bonding. This would be a utility tariff issue.
