How would you design a infinitely scalable language?

So suppose you had to design a new language from scratch and your goal is to make it "infinitely scalable", which means that you want to be able to add as many features to the language as desired through time. How would be the initial core features to make the language as flexible as possible for future change? I'm asking this because I feel that some initial design choices could make changes very hard to accomplish, so you could end up stuck in a dead end