The higher current draw (if a low voltage DC is used) will require much heavier cables than the typical (for US) 12 guage cable. That can get expensive and there would certainly be the need for DC-DC converters for funky voltages. Maybe it would be standardized over time but that's a long way off.
Maybe there will in fact be something like a 48V standard that would be some sort of compromise, although I think the Tesla batteries run around 220V to keep the motors relatively small. I don't know if there's any real problem with running higher voltage DC in the home although I'm pretty sure switches would need to be made differently to prevent arcing.
Seems like maybe more trouble than it's worth.