Oddly enough, I've actually had this happen, all three generators tripped off just prior to V1...one quickly restored due to quick action of the Flight Engineer.
What to do if at/near V1, if heavy/WAT limited?
Continue, absolutely, using the standby instruments, which is what they are there for.
Sliding off the end is NOT on my list of available options.
Period.
PS: I've also had both attitude indicators go TU just at rotation...just what the standby is installed for, but you sure don't want to depart with a depleted ships battery, otherwise, up the creek without a paddle...on a dark night/IMC.