I like your question and I am interested into other answers as well. I think the answer depends on the role you want to fit in.

I can tell you, that I will learn portuguesse in 2020 as my longterm goal is, to live in portugal and I will set the right foundation next year.

Depends what area you work in but as you are on this site I assume it's something nerdy :) I would like to be better at graphic design, nothing to complex, just the ability to design better icons, favicons, button graphics, blog post banners etc.

I want to actually make an IDE in the coming year - I've been thinking about it for months and just need to dive in

1) Learn to code

2) Read at least 50 books

3) Study new languages, for me it will be brushing up on Italian and starting studying French

Better Finance skills, meal planning, creating good habits for completing side projects

sprite and tileset design for video games

learn Gamemaker Studio

financial discipline

civic participation and community organization

meditation

cooking

physical fitness

empathy

webapps security