Your question is well researched and well written, but if there's a reason it's closed I think it's because of these two quotes:
I'm wondering how I - as a 20-something today - can start to prepare myself to do the work that these experts refer to in the years running up to 2038. In other words, what specific work will said "lucrative contracts" actually involve doing?
And:
What technologies/languages should I start learning now to prepare myself?
I feel like several really good answers to these questions could be submitted, so no problem there. However, my guess is that they would involve a significant element of subjectivity, i.e. I think you'll best position yourself by learning X and doing Y, followed by another answer saying the same thing but with a different X and Y.
Therein lies the problem. How can the community decide which answer is correct? Not correct for you, but definitively correct--for you and others with the same question. I don't think we could. That makes the answer only useful for you and unfortunately not a good fit for the Q&A format of the site.
You would improve the question by dropping the text of the second quote. You would probably need to reconsider asking what specific work "lucrative contracts" would involve as that might require too much conjecture on the answerer's part, though I'm not certain because I don't know the answer myself.
Perhaps some others could provide more feedback to help you determine whether there's still a core of your question that would be on-topic for Super User.