Re-Tooling Your Skills for the Future?

nojayuk asks: " Over the decades I've re-skilled myself several times, from mainframe FORTRAN through minicomputer PASCAL to microcomputer C. In between I've done microcontroller development and programming in Assembler, robotics, graphics design and 3-D animation for TV, PC build and repair, Website design etc. Currently I'm looking for work and I'm wondering what new skills do I need to stay in the computing biz. What OSes do I need to know, what technologies do I have to have under my belt for the employers to come hunting for me instead of me passing my obsolete CV around and being told to get lost? I'm looking for advice, not just for next week but for a few years down the line. What can I do to acquire these essential new skills?"