Market wise, Java is still popular in the Enterprise and of course if you are developing for Android, you’re going to probably use Java (I’d rather use Kotlin), but for backend work the three most marketable languages seem to be JavaScript (Node), .Net, and Java.

Yeah PHP jobs are a dime a dozen but they don’t pay well. Python is a little better but it’s not “Enterprisey” enough for major corporations and the cool hipster companies where all the money is going are using Node.

I don't know where you're getting your information about Python from. It's popularity has skyrocketed in recent years. Search Indeed's API for title:python and location:London. 412 Python jobs compared with 278 for Node.js. What's also interesting is that there are currently 35% more Django jobs than Rails in London whilst at Angel.co they're about even.

Well, if I ever want to move to London...

As I said, there are also plenty of PHP and WordPress jobs, but those aren't exactly paying top dollar either.

If you have to tie your horse to something. It makes the most sense to tie it to JS. Until something takes over JS on the browser, it's going to stay marketable. Then you consider Node for the server and the frameworks that you can make good enough mobile apps with JS has both marketability and flexibility going for it.

Then add TypeScript on top of it, you have a mostly strongly typed language.

As (primarily) a node user, there's way more data science an ML in Python than there is node.

If you're still tying your horse (and haven't already) it might be better to skate to where the puck is moving - Elixir would be a good example.

Which puck is that? There are very few Elixir jobs on most of the jobs boards I've seen and let's be fair - Elixir has now had long enough to build momentum. From the numbers I've seen Elixir clearly seems to have been eclipsed by Go.

There are no jobs for Elixer in my market.

Python is definitely something I’m going to keep in my tool belt if for no other reason AWS, Boto3, and Python go hand in hand.