Seriously, what is up with that ending? It's very open-ended. The Time Traveller disappears and never comes back. We don't know where he went or why. The unnamed narrator makes some guesses to show the range of possibilities: maybe he's with our primitive ancestors or dinosaurs (not at the same time, of course), or maybe he's in the nearer future. Which all basically means that we don't know where he is or why he hasn't come back.
It's curious that the narrator's main concern is "Where did the Time Traveller go?" not "Why didn't the Time Traveller come back?" While the questions are clearly related, this epilogue keeps us focused mostly on the issue of time travel and keeps us away from asking what happened to him. (Is he so happy that he decided not to come back? Did the Morlocks eat him? We'll never know.)
The ending is not only open-ended when it comes to the Time Traveller's fate; it's also somewhat open-ended about the moral of this whole story. While the Time Traveller is pessimistic about the future of humanity, the unnamed narrator finds a way to be somewhat optimistic. He notes that, sure, something will be lost in the future (little things like "mind and strength"), but certain essential parts of humanity will remain (like "gratitude and a mutual tenderness"). Even if he is incredibly optimistic, though, it's unclear what the narrator thinks is worthwhile in the final part of the Time Traveller's story, where he sees the almost totally desolate beach.
Ultimately, the ending is pretty ambiguous, and critics have come to different conclusions about whether it's hopeful or hopeless. It seems as if Wells has purposely left this conclusion as open-ended as possible – perhaps in order to leave the final decision up to us.