Rip van Winkle is a humorous cautionary tale. I may have a slightly different take. I think it is about wasting away your life, and letting the world pass you by. So many people just go about their daily lives without really experiencing what the world has to offer.
With the beauty of the Catskills and the quaintness of the village before Rip's enchanted sleep, Washington Irving expresses his love of Nature and his nostalgia for a slower, less contentious time. When Rip van Winkle returns ot the village, he is met by a din of harangues. He remembers when people sat leisurely at the inn, not haggling about political issues.
I want to present another interpretation of the "point" behind "Rip Van Winkle": the glorification of setting. Rip Van Winkle has a very distinct setting: the Catskill Mountains. Take a look at the following excerpt:
When the weather is fair and settled they are clothes in blue and purple, and print their bold outlines on the clear evening sky; but sometimes, when the rest of the landscape is cloudless, they will gather a hood of gray vapors about their summits, which, in the last rays of the setting sun, will glow and light up like a crown of glory.
This is the place where Rip has his unusual experience, and part of the reasoning behind the story. The reason why I am presenting this more unusual concept is because my uncle and aunt live in the Catskill Mountains, ... and they will be the first to tell you what this story has done for tourism of their area. Whether Irving meant it to be the effect is irrelevant, ... but over the years, the "point" of the story has shifted at least somewhat to this arena.
I agree with both of the above posts. There is a bit of politics in the story (though I do not think it dominates the story). I think that the dominant point of the story is entertainment.
In addition to entertainment and politics, I think that gender relations is a major point in the story. One of the things we see in the story is how Rip hates the way his wife (in his view) nags at him and how much more free he feels when he wakes up and she is gone.
So, I think there is an element of politics and an element of "don't waste your life" and an element of commentary on marriage. But those elements are wrapped up in a story that is really meant to be a fun read.
I think that the end message of Irving's story is actually a political one. There is much in the story that indicates the need for individuals to maintain connection with their political communities. Rip is out of place in the new world because he, literally, slept through the American Revolution. When noting the "change in character" of the people around him, this can be Irving's way of suggesting that individuals who are not turned on to politics may have politics turn on them. Rip is out of step with his political community because he never actively identified himself as a member of such a community. While Irving faced charges of unpatriotism with how he ended up developing his character, I think that there is a strong suggestion about how individuals lose a major part of their social and personal identities when they fail to acknowledge the political component of them. While the overall "point" of the story might be to stay awake- literally- through live, I also believe that there is a calling out for individuals to be aware of their political state of being so thath they are able to do something about it.
I deem Washington Irving's intention in writing Rip Van Winkle was to teach his readers a lesson as well as entertain. Irving is revealing to his readers through this story that if you live an inactive life, never accomplishing anything, and are always contented with the bare minimum life will pass you by.