I agree with most of this. But I don't think GiftWraps make spam filtering impossible. It's just a different way to do it. Because the event is private, the relay must rely on Reports (or Deletion events) from the author of the p-Tag that the GiftWrap is sent to. Clients can help relays filter these events out when they are in-fact spam. 

I think people are waaay to stuck on the current way of filtering spam. Also, I expect to see relay operators that will only deal with GiftWraps. And I would go further to say that they will become the most used relays because most of the information traveling through Nostr will be private in the future. 

To me, P2P is now a must. If we truly care about decentralization, P2P should be an option in the toolkit. Relays will always be there as a fallback, but they don't need to be the only game in town.