Relevancy doesn't really matter much in Smash. Yeah, Sakurai does sometime choose characters or things because they are relevant, but removing a character for not being 'relevant' is stupid. Every character in Smash has a fanbase and Sakurai knows this and wicely does not like removing a character (unless he has to, of course).
People always find so many weird and often dumb reason for specific characters to be cut (Nintendo wanting to get away from the Wii branding, so of course Wii-Fit Trainer and Miis must go. Too many swordsmen, so of course a whole bunch of them need to go. Third Party characters are evil, they have to go. Etc etc).
I am sure characters will be cut eventually, for future Smash games, but I am glad Sakurai takes this chance to bring everyone back.