I just saw on a publication that 1st rank wallet was Satoshi Wallet, with 1.1 million BTC in it.
FYI, it's just an estimation which popularized by this old blog post
https://bitslog.com/2013/04/17/the-well-deserved-fortune-of-satoshi-nakamoto/.
Any one have an idea of what can happen if theses 1.1 Million BTC are sold at once ?
These are the common speculation if Satoshi attempt to do it.
1. Centralized exchange would freeze such massive BTC deposit, since it's unusually huge.
2. If Satoshi managed to sell all of it, Bitcoin price will crash and some people will lose trust towards Bitcoin and cryptocurrency in general.
Is bitcoin in danger because a wallet hold that much ?
No, since Bitcoin use PoW rather than PoS. Satoshi can't use the 1.1M BTC to manipulate block generation.
Do you think theses bitcoins are lost for ever ?
I don't know. But there's no sign it's being moved after 15+ years and Bitcoin price reaching above $60K.