This seems a rather mercenary outlook to me. You are asking for suggestions on how to spend your spare time with the goal of keeping yourself employed, without regard to whether you would enjoy the subject or process.
I'm all for goal-driven careers, but studies show that the most successful people are the ones who like what they do. It largely doesn't matter whether the skill is the most "in demand", it only matters whether the skill is in demand "enough". This is illustrated by successful people in (what we would consider) pedestrian careers such as furniture sales, property rental, or owning the local laundromat (which, BTW, is the most common way to be successful).
The first step is discovering what you enjoy. The easiest way to do this is to spend 1 hour in quiet solitude. This is unexpressibly difficult if you've never tried it - you need a situation which has no interruptions whatsoever (kids, phone calls, other people), and you need to stick with it for the duration. Solo long road trips, long walks, hiking, and biking work well for this.
For the first 1/2 hour your head will be full of day-to-day thoughts, reminders, personal maintenance, reviewing memories, and so on. After awhile, this will quiet down and your mind will start to wander. Whatever you think about most is likely your source of joy.
Figure out some skill that feeds into your joy, choose a project that requires this skill and which also feeds into joy, and resolve to complete the project by the end of summer. Write the goal down (this part is important!) with as much detail as you can, stick it in an envelope, and put it away for later.
Your brain has likes and dislikes, as well as a goal-setting mechanism that you can use to your advantage. If you want to be happy, you should start the process of being happy right now, while you still have leisure to do so.
(Oh, and to answer your question: I'm writing a paper on hard AI.)