jimmy and Cindy do not get together but they almost do. To be more specific if you watch the episode Lady Sings the News they are basically a couple by the end. It never may not officially say that they were a couple but he kisses her and they walk off holding hands as the credits start rolling. Somethings just don't need to be said.
That was the last official episode of the series. The director stated that the Jimmy Timmy power hours were not part of the cannon so they don't count as far as Jimmy and Cindy's relationship in the cannon is concerned. Also it was stated at some point that Jimmy and Cindy were meant for each other. She was intended to be his wife. If you research the old interviews you'll find that info.