Maybe not exactly new, but hot and for sure something you don't want to miss and probably don't know yet: Learn how your operating system's network stack works

Maybe not exactly new, but hot and for sure something you don't want to miss and probably don't know yet: Learn how your operating system's network stack works, how you can manipulate behavior with sysctls or kernel arguments, maybe dive into stuff like the BSDs. Also you may want to extend your horizon and get into nginx, smtp, shell scripting, etc., if you don't know them well. All of those offer way more than the basics and things can come in handy. You might want to go into the field of virtualization, but please don't start out with Docker. Docker is nice, but you really want to understand the basics first (LXC, virtualization in general). There are awfully lot of bad Docker setups, just because it is hot. Another thing that one can spend quite a while getting into is uwsgi. One can use it for way more than managing Django or Flask applications. Securing services with SSL is also something a lot of people seem to do wrong, so actually understanding the details of what you do might be something you might want to dig into. When it comes to DevOp tools you might want to take a look at agent-less alternatives to Puppet (Ansible, Rex, cdist). Another interesting thing is logging. The Elastic Search/Kibana stack is hot and relatively new (at least the latest/upcoming release of Kibana).