My question is what will happen if ledger site goes offline completely and the owner disappears, will the wallet still function? even in 1000 years?
Since you'll also have the seed, you should be able to get access to your funds - with ledger or with something else - even in 1000 years.
So you can use Ledger as long as it works, make sure you keep the seed super-safe and you'll look for alternatives when the Ledger will stop working.