It looks like clients will get more complicated over time to cover as much Nostr functionality as possible and do some algorithms for better feed, and relays will get as dumb as possible for speed and high online user count.
Discussion
Beefy relays are going to be more attractive because noone wants to miss out on events.
There may be beefy read only servers that syncs with all other normal servers and collect unique events, that will ensure all the events are there. Writing can be done still be done to several smaller servers..