We will never get a real estimate before stake.com announced it and it looks like Stake.com will not do it for privacy reasons
Based on unofficial sources Hackers managed to steal 430K customer data  including email and maybe also KYC information
Another source said they stole at least $10 million from the hacked account, but this one is rather difficult to believe.
Luckily I was late to check the email and not click on the link sent to my email.