The SoK paper by Bonneau et al provides a good overview of the state of knowledge (as of 2015) and research directions for Bitcoin. Is there anything similar for Ethereum?
The knowledge and research is actively developing so there may not be a single academic paper, and you will find similar material on Github:
- https://github.com/ethereum/EIPs/issues (Ethereum Improvement Proposals)
Gitter is also active:
Time to admit that the real purpose of asking this question was to answer it with my own paper.