obviously, schnorr signatures are on deck. that'll allow for cross-input aggregation to make coinjoins indistinguishable from regular transactions. that's a pretty massive development given that exchanges are beginning to target coinjoin users. estimating based on segwit's activation timeline, that could happen by early 2021 or maybe even the end of this year, optimistically.

but "useless"? that's quite a strong word.

confidential transactions (CT) to obfuscate transaction amounts seems like an attractive next step. but my understanding is it requires extension blocks or a hard fork. so.....probably not gonna be implemented at the consensus layer. there's always sidechains though. liquid (blockstream's sidechain) supports CT for example.