What remains is the basic idea that representations in general are to be constructed by parabolic induction of cuspidal representations. A similar philosophy was enunciated by Israel Gelfand, and the philosophy is a precursor of the Langlands program.
The core concept that persists is that representations in general are built through parabolic induction of cuspidal representations. A similar viewpoint was expressed by Israel Gelfand, and this philosophical stance precedes the Langlands program.