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 much of an 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 12, 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 12, 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."

At Minecon 2012, Jeb was asked about Red Dragons. He acknowledges that the Dragon Egg item currently has no use and that it is possible to be used for Red Dragons. He explained that one of the main reasons they are not a high priority to add is because coding them would be difficult. He also makes the example that Ender Dragons fly through terrain as a workaround for the type of coding Red Dragons would require.

Around 1.7 Pre-Release when asked if red Dragons were added Dinnerbone said they were never promised and they have no plans for it

In a Reddit AMA Dinnerbone said "I'm sure one day there will be. Not right now though."

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!"
 * The winner of the Minecon 2013 costume contest was a Red Dragon