Red Dragon

The Red Dragon is a new mob that is planned to be included sometime in the future. But still, Notch has not hinted an arrival date- and Jeb, who is currently in charge of Minecraft development, has not shown major interest in adding them.

History
Originally, Dragons were a possible planned mob hinted at by Notch during the Spider Jockey update. He also mentioned that dragon lairs may be an addition. They remained a potential work-in-progress until the Ender Dragon was announced.

On October 12th 2011 Notch announced Red Dragons "After release, I will totally work on slightly less dangerous dragons that don't destroy terrain and can land and whatnot. They will be red."

On October 12th 2011, in a Reddit post Notch also said. "They will be different dragons. The Ender Dragon will probably become larger, and the ones in the main world will be this size, won't go through terrain, and will be red because dragons are red."

Trivia

 * One of the game's splashes (as of Minecraft 1.0) states "Kind of dragon free!", joking at the original text of the Beta and Alpha versions of Minecraft which read, "Absolutely dragon free!"
 * In the Ender Dragon's folder (within the mob folder), there is an image named dragon, showing the texture of a dragon similar to that of the Ender Dragon's, but gray rather than black, hinting at the possibility of other dragon types