Well as i can see that many of the replies are about how hard it is, i do understand that, let me give you an example of bitaddress.org which was used by many people back in the day to buy bitcoin, what are the chances that someone made a wallet and transfered some bitcoins to it and forgot about it, i can refere you to this https://www.reddit.com/r/Bitcoin/comments/1rli5i/if_someone_cracks_bitaddressorgs_number_generator/

but again maybe the fact that there are +30million wallets without hearing about one wallet collision is proof of how impossible it is. and my point with this topic is that people who say 2^256 and discounting the amount of wallets that are out there with a balance so you're not targeting one wallet but +40mill and growing amount of wallets. maybe oneday it will be billions of wallets.