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.

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!"
 * As Notch stated, he might add dragon lairs. It is possible that these would spawn in strongholds or inside Extreme Hills and cliffs. It could be possible that the The End is the Ender dragon's somewhat lair.
 * Red Dragons will be "slightly less dangerous."
 * Sometimes when exploring tunnels, you will find a dead end that looks like a big cave, about the same size as the Ender Dragon. This could hint that the dragon lair is released, but the mob is not yet created.