Personally I was looking on Notch's Twitter.
you can look too, well apart from his tweeting to his fans too. http://twitter.com/#!/notch

I don't particularly want an Ender Dragon in the overworld, considering they rip through terrain like nobody's business:


Red Dragons, on the other hand, I think should spawn somewhat similarly to King Slimes in Terraria - Random and rare, some distance away from your spawn.

It's good to see something rather challenging in Minecraft for once - Yes, it can be tricky at times, but I've been playing this hardcore world for two weeks now and I'm yet to fail. These will probably make for some good group-fights on servers, with five people going in with merely their fists... Again, like bosses in Terraria ('Cept a bit harder to hit)

Oh, I wasn't talking about Enderdragons, those are for the Ender Realm only man.

But yeah the whole concept of the dragon as a "boss" that requires a group fight should be really interesting.

Dragons, apparently the king of griefers in Minecraft, that is if they got on the overworld haha.

But in all seriousness here, I for one am absolutely stoked about Dragons coming to Minecraft! We know how to deal with your growling Zombies, exploding Creepers, jumping Spiders, rattling Skeletons and the creepy Enderman, how about something soo large and gigantic that it'll throw a whole new type of challenge for players? I think if it ends up being in some new "realm" of sorts for these "Ender" species, that would be pretty nice... especially if there are some nice goodies there for exchange of defeating something that can kill you with a few swipes of his claws. I cannot wait to see what Notch does with this new (and rather adorable) beastie, if it'll be a "boss" or just some super-duper rare menace.