The research in CS is very active. Take a look at arXiv/cs to get a sense:

https://arxiv.org/list/cs/recent

I would say Machine Learning is particularly "hot" right now, with the anecdotal evidence being that many ML conferences (like NIPS, ICML, CVPR, etc) have been experiencing better than linear growth.

I'm not a computer scientist, but I'd say Quantum Computing, Crypto Currencies, Compression algorithms like HEVC, new programming paradigms as can be seen in Escher, the comeback of functional programming and microkernels seem interesting to me.