This wasn't a plot point of the episode, more of a subtle nod towards deeper stuff. I can't really say too much without spoiling it for you, but I'll say that I didn't even notice this in the episode until someone pointed it out.
I don't think they could've done it any better in the episode. Even though Applejack says they'll probably be too "busy" to all come for the next reunion, her body language suggests she's thinking of the other meaning of "not making it." Saying that someone might not "make it" is an allowable euphemism for death that cartoonists have used for decades.