I can't imagine Luke is really the last Jedi.
Maybe it is the disgruntled Expanded Universe fan within me saying that, though.
Yoda: Last of the Jedi will you be.
Even if you make the claim that he's wrong and that other Jedi survived, it's possible they just aren't doing Jedi things anymore. A retired Jedi is no longer a Jedi.
Luke tried training more Jedi but they all got killed by Ben. So right this moment, Luke IS the last Jedi. He'll probably pull a Obi Wan and die to Rey will become the last Jedi.
Which kinda mirrors the Sith just sacrificed instead of usurped.