Nostr is only Nostr if clients implement the so-called "outbox model". If they do that then there will never be pressure to use centralized relays.
Of course anyone can implement a thing that looks like Nostr but actually isn't, but at least we should have the definitions clear and prepare the terrain while we have time so anyone will be able to spot any so-called "client" that isn't implementing Nostr correctly if they come.