Permissionless access to the Farcaster social graph to identify people you regularly public interact with (and who interact with you back) is the new contact sync.

Not a perfect replacement, but pretty good. 

Just need to scale it. :)

Now if we can just get a client that builds that graph by focusing on connecting you with people who have common interests as a social network vs social media based on popularity of particular users then it could explode. 

People want to socialize with others they have things in common with, not just be broadcast to by people with big followings and ignored when they try to interact.

FoaF and tracking/promoting engagement with particular topic content (vs whatever certain people post) would really help in that regard.