What a great title!!!! (Or "How to cause an immense disturbance in the Fandom!!!"
To me it signifies that the film IS all about the last Jedi currently alive in the SW universe ,ie Luke Skywalker, rather than actually forecasting his death. Lets be honest, who as a SW fan ,isn't just a bit desparate to learn what has happened to him over the last three decades.
As "THE LAST JEDI" so much depends upon him and it would be such a great story if, by the end of this trilogy, we actually see him bring about this much talked about prophecy of bringing balance to the Force though new discoveries.
In that way the title nicely ties in with all this speculation over "grey" force users. Perhaps we will see a new name added, neither Jedi or Sith but something else.