What can be done in order to improve privacy in bitcoin transactions?
Pieter Wuille posted an answer earlier today that covers some of what is already being explored in the pipeline for additional privacy.


  ... but improvements are continuously being worked on (search for things like MAST, TumbleBit, Layer-2 payments, Taproot, signature aggregation, scriptless scripts, confidential transactions, ...)


In addition, further ideas like change obfuscation have recently been seen on the [bitcoin-dev] mailing list.

There will no doubt be even further suggestions in time.