I follow the language specific sub-reddits, and I read release notes for major releases of languages (so for python that would be 3.X) even if I wasn't going to jump to the version set.
_This_, so much.
If you are a heavy user of a language / library, it's immensely helpful to look at the release notes every once in a while. Even if you don't plan to upgrade now, it gives you an idea of where things are going (and may eventually tip the scales to a "fuck it, it's now worth upgrading" moment).
For Python specifically, PEPs are also a good way to keep track of what's happening (even if some of them don't get accepted): https://www.python.org/dev/peps/ ; there's also an RSS feed: view-source:https://www.python.org/dev/peps/peps.rss/