When Yoda died he left behind an unfinished Yedi Luke, maybe close to his Bachelor but far from Mastership. So Luke never was a proper Yedi, even if the spirits of three did accompany him. Ever since that scene of Yoda’s death I asked myself how could the Yedi’s now ever continue?
Chances are Luke would fail in training his first scholar. That scene where it says:”The Force is strong in my family. My father had it, I have it, my sister has it. You got it, too.” He would not say those words to a family member but to someone he wants to give faith in the Force and in his knowing about.
Ben failed with his first scholar. Why should the unfinished Luke do any better?
See that scene where he says my sister has it and a hand from someone who looks like laying on a bed is handing a light-sabre to a woman standing when the words:”My sister has it”, are spoken?
Luke either dies or is a broken man who retreats into exile after his scholar — as incomplete as he is himself — has turned to the dark side. Those left to fight for the Light side are the kids of Lea, themselves untrained since their mom never got any.
This is the only point where your analysis makes sense: When Yoda says that everything is lost now, he refers to the Yedi tradition. No finished Master training, no more Yedi master. When Luke tells the emporer that he is a Yedi like his father was before, he reminds us (now that we know episodes I to III) that he is incomplete, too. Luke has three spirits guiding him of those Yedi who died when he was present. But does that make him a good teacher? Can an unfinished Bachelor raise a full Master with the help of some good spirits? Doubtful!
“I am nobody”, could fit someone hiding a treasure and herself. Lea’s daughter, with not enough energy to become a Yedi, yet with enough to protect a Lightsaber and to hold inside the spirit of uncle Luke ( in case he dies and does not immigrate to where his former scholar can not find or sense him; note that this makes sense for there seems to be a nighttime Lightsaber duels in a forest of what could be Yoda’s home, were Luke retreated to and which is my version that he hangs with R2D2 as a broken man in the swamps trying to find what his education is lacking, this time ignoring the outside pains in true Yedi fashion).
Now if this plot looks too much like history repeating to you, then remember that it probably does in the mind of Lukas and that Hollywood studios these days do not pay for risky scripts or unproven storylines as Robert Zemeckis pointed out when interviewed about The Walk and Back to the Future. So a failed teacher and a generation looking for orientation without knowing fits in. Fun is, their best teacher in the absence of a true Yedi seems to be Han.
Always remember: At the end of episode VI, there had only a battle been won. A battle which left behind a huge army of Clones programmed to follow a dead Sith Lord. And since I doubt that the Republic could hand them back in return for cash or coupons for new Clones, I am sure we have a very rough, rogue and sense-seeking universes awaiting us -
even more sense-seeking than us, who try to read 100+ minutes of movie plot from 7 clever edited minutes. :-D