You need to make a distinction between hot and high-priced. What drives a high salary is not how much demand there is for something, but how much demand there is compared to the number of people with that skill. Python, PHP and Java are poor choices in this respect, because while there is high demand, there are also a lot of people with those skills. Web development in general doesn't get the high salaries.
If I had to pick a skill that was highly likely to net a high salary, I'd go with COM programming in C++. For years nobody has been learning COM, and as a result the only people still in the field are senior people. It's still very much in demand, and that demand isn't about hype, its about necessity. Knowing how to program Extended MAPI doesn't hurt either.
What you need to be looking for are unsexy technologies that are in reasonably high demand. Others have mentioned SAP, but there's also Cobol (pretty much anything on IBM iSeries), business intelligence, and Delphi (in some regions, and only for more than form design). Inside each platform there are also niches that net you salary bonus points. For example, knowing the ins and outs of writing PHP applications and setting up PHP environments that perform well when scaled to thousands of concurrent users is a valuable trait.