Current blockchain hot topics in research
I think it's scalability. The cost to generate a block is getting more and more expensive. Couple months ago, CryptoKitties caused Ethereum network congestion due to the surge of transactions. For real world application, I think blockchain must be able to handle high volume of transaction. This can be achieved by reducing the cost to generate a block. AFAIK, some blockchains are developing proof-of-stake algorithms replace the old proof-of-work one.

You may interested in Ouroboros proof-of-stake algorithm, which is implemented by Cardano. Ethereum is also working on their own implementation - Casper