The last few sentences are when Kennedy gets philosophical and energizes the crowd one last time. He wants to inspire change without actually promising to change anything. He isn't talking specifically about Berlin and the wall anymore, but rather about a wider idea of how mankind is connected.

The speech ends with a final repetition of his statement from the opening line, "Ich bin ein Berliner," applied to the whole world and giving closure to his speech.

Talk about a memorable last line.