You would still need the compiler to be written in progsbase too: is it? As I am not quite sure (and you cannot gamble on it) that Java and Java tooling is still there in 100 years. Which then brings you back to Haxe ; kind of the same gamble there but that is open source which makes it longer lived generally anyway.

A language for the ages would be a Forth imho; you can write the language on the back of a beermath and it takes mere hours to implement on whatever system.