Well I don't really want the final episode to be a closer. Why? Simple, because it would mess with the story. First of all, the creator has announced that the movie is the end of the SpongeBob canon, meaning that, story wise, it takes place AFTER every episode, even episodes that are still being made.
Now what if the final episode was a closer, like some people want it to be? Let's say that Plankton and Mr. Krabs become friends. But wait, then comes the movie! Why would Plankton suddenly turn evil again, and try to steal the formula again? It just doesn't work.
But then someone could say that the final episode can take place after the movie, right? Nope. That's not going to happen. If the people making the show did that, then there would have to be a WHOLE LOT of changes in the final episode. First of all we'd have to have SpongeBob as the manager of the Krusty Krab 2. Second, Plankton would have to be in jail, crossing out the possibility of becoming friends with Mr. Krabs. Third, Squidward would probably be nice to SpongeBob. Think about it: at the of the movie, he was proud of SpongeBob, so surely he wouldn't hate him anymore. All of this has to taken into account with the final episode.
Of course, this CAN be done. But think about it. We need SpongeBob as the Krusty Krab fry cook, Plankton being evil, and Squidward a jerk, up till the very end... well, at least untill the end of the episodes (after that, the movie is free to make changes for closure). It just wouldn't be as entertaining, not to mention that there will surely be people watching the final episode, that didn't see the movie. There would be jokes that people just plain wouldn't get.
So that's basically why I would rather not see a closure episode. Now as for me? I don't know what I'd want to expect. I know that I would want to see a special, maybe an hour or a thirty minute episode, and full or laughs and excitement. I will want it to have a great ending, so that the series can go out with a bang. Also, I think it would be cool to make a joke or two about Mr. Krabs opening up a second Krusty Krab. It would be covered up as a joke for everyone, but then for the people that saw the movie it is actually a clever reference to the movies storyline that comes up next in the story. Also, I just have a thing for the movie, its plot, and the idea that it is a great ending for a great series.

When I said I couldn't picture it being the last episode (or whatever I said), I meant that I don't think the writers would have enough brains to think up something like that.

Ooooohhhhhh. Well thanks! I really like your ideas too! They're really creative! It seems like everyone's ideas are better than what the writers ever thought of!