I expect that everyone is aware of the just past 40th anniversary of the Moon Landing. I hopped in my car to go have dinner with some friends and caught the tail end of some news story and thus missed the name of the speaker being interviewed. All I heard was he said that he many years ago when he went into schools many hands were raised when he asked how many students wanted to be astronauts. Now he says there are just a few and thus he is concerned.
It seems to me he is asking the wrong question; why not ask "How many are interested in living for 10 or 20 years or more on the Moon or on Mars or on a space colony?" and see how many hands are raised. I do not know for sure how many will be raised but at least it shifts the frame of the discussion. It appears to me the one of the reasons the astronaut question gets such a low response is that there might be a perception of not much change over the decades and that the space program is stagnant.
Plus consider the limited number of astronaut slots. But there are obviously going to be a lot of colonists slots. But will NASA be in the lead in establishing human colonies off earth; not likely because that is not what NASA has been directed to do. And NASA is probably not the proper organization for space colonization. Actually I think the most likely way for it to happen is for the private entrepreneurs like Scaled Composites to lead the way. Maybe they know the questions to ask.