All we know for sure is that the scene takes place sometime in the future on some planet.
The scene though is a little complicated to talk about beyond that because there isn't much in the way of explicit information, so everything has to be inferred from the context of the ending. Which means that the meaning behind the scene changes depending on whether or not you're talking about the end of ME3 before or after the release of the Extended Cut.
In the original endings the Star Gazer scene makes more sense. Since it is heavily implied that activating the Relay network caused the Mass Relays to explode -- thus resetting civilization -- the Star Gazer scene is meant to show that life recovered in a universe without the Reapers. In this context the scene takes place long into the future, owing to the fact that they're talking about Shepard like he's a myth.
Post-EC the scene doesn't really fit. Since the epilogues show that the destruction of the Relays was only a temporary issue, the tone of the Star Gazer scene doesn't really make sense (since they are still talking about Shepard like he's a myth and space travel as if it isn't common place). The scene isn't needed to show that life recovered because the epilogues already do that (unless the Refusal option was taken). The only thing I can think of is that it's supposed to be something tying back into a theme of exploration and new beginnings. It could also be a tie in for ME4 (like the kid is the protagonist in the next game). Somewhat jokingly I say the scene is there to show that the Catalyst was wrong.