I just had a friend telling me that even if one manages to get a key, there is no longer a possibility to even create an account for the old game.
That’s not exactly true. It is still possible to create an account for The Secret World with a Funcom key. It is not possible to make an account with a Steam key, and it may no longer be possible to get a Funcom key from your Steam key as “The Secret World” no longer appears in the Steam client.