Well, to answer the question precisely as worded then assembly. It’s one of the only languages that can effectively communicate with hardware at its lowest level. I don’t know of anything that could possibly best that.
Edit: and there is no way in hell C# will outlive C ;). C# is essentially a wrapper that builds off of the C standard. Aka, C is a prerequisite in order for C# to thrive. If the C standard doesn’t adapt then not much can be done in the way of C#.
Now, as for HTML… I don’t care what version it’s on. Languages adapt. C isn’t the same C it was a decade ago for instance. Programming standards change. HTML is another iteration. Nothing enticing.
JScrjot is almost laughable. It’s a rather simple programming language that even Forest Gump could figure out. Doesn’t make it bad by any means. But I don’t see it overtaking PHP any time soon. What you learn in school doesn’t often apply in the real world.
Now… As for finances. Work will overtake most of your life. Would you rather be miserable most of the time and get an occasional trip to the beach or be happy and love the work that you do ;).
Good luck finding that super language. But as I said… No language is future proof.