When they started talking about dreamers, finding people who don't give up, that sounds very touching. But when you begin to think about, what they want the dreamers to do, things get a little complicated.
Tomorrowland exists because "dreamers" , "elites" want to find a place without pxlxtxcs to dream, to make the world a better place, just like the question David asked Frank at the beginning, "how does it make the world a better place". Then, why they decided not to make THIS current world a better place, if they are really "dreamers", "elites" that can change people's lives? Does pxlxtxcs have such a huge power that stops them from changing THIS world? Or the cruel truth is, they decide to leave behind those who are not "dreamers", "elites", isn't it?
(furthur thoughts: trying to compare between WALL-E (programmed to) stay to save the place and Heroes' Reborn create another world..)