Foreign translation of the title of Star Wars: Episode VIII – The Last Jedi's title have revealed one huge bombshell of information: the word 'Jedi' is actually pluralised, meaning that there's more than one.
In German, the title translated to Die Letzen Jedi (thanks, IGN Germany), whilst in Spanish it's Los Últimos Jedi (thanks, Engadget). Both of these are pluralised, confirming that there will be more than one Jedi in the film.
Now we can only speculate about which Jedi aside from Luke will be in showing up. We can assume that Rey, and possibly Finn, will undergo Jedi training at one point, so the title could presumably be referring to them. It could even be referring to other Jedi that we don't yet know of, so I guess we'll have to wait until December 15, 2017 to find out.