They were even thinking about requesting blockchain rollback (that possibly means making fork and paying to miners to follow that fork instead). If that would pass, that would really doom bitcoin as is.
Rollbacks can be considered for shitcoins, in Bitcoin it is nearly impossible and very unrealistic.
I wonder what would have happened if the hack were 4 Billion instead of 40m, would Binance have the power to rollback
Not nearly enough power or impact for that. The masses of miners who could roll back will not care for their plight and even billions stolen is worth less to the community and miners than making sure all transactions go through. For example; imagine what else is on that block chain they'd have to also kill? How many times exchanges been hacked and no re-dos? How could bitcoin keep it's status as super-solid if they allowed such things and it's only that status which gives it value? Totally untenable for bitcoin.