The file size increase will continue to be an issue for a long time. As hard drive space started becoming cheap enough for PCs, people started wanting their songs on phones and MP3 players, where the storage was still expensive. As phones are now starting to get cheap enough internal storage for the flac file size not to matter, people are starting to stream music, where the file size is again important, as people are streaming music through cellular, where the price per gigabyte is still high.

Maybe, once most people, even in the third world, have unlimited data plans, music file sizes will stop mattering. Or maybe we will have moved on to something else entirely where big files is still an issue. Maybe people will want to stream music from earth to space stations or lunar bases, I don't know.