No, I do not lnow that for a fact, please provide 100% evidential proof of otherwise... thought so.
Alright, let's anolyse this so-called leak:
http://gamersanonymous.ca/skyrim-dlc-expansion-leaked/
Starting off with the words "three massive expansions" along with minor add-ons, okay, it's feasible (although I personally think they would do more bigger ones and almost no smaller ones, as promised.
Going to Hammerfel seems feasible, if it weren't for the fact that Bethesda has never let you visit another province as they reserve them for future games. So going to Hammerfel? Unlikely.
Next up is the so-called "dragon taming", which would allow you to ride a dragon. I'm aware that there's a scene where you ride a dragon to Sovengarde, but that's 100 meters up in the sky, you can't control anything and it's really just a dummy on the dragon, proven by your crosshair staying still in place and not disappearing. Secondly, just even think about the limitations this poses. Have you considered how they would possibly even land a Dragon? The world geometry is far too complex too do that. Trees, rocks, houses, villages, virtually everything will be in the way. If it would be done, it would be done extremely buggy. Thirdly, using weapons and magic while riding one? The controls won't even allow it.
Then they mention "other" mounts like sabre cats, mammoths, bears and wolves. Okay, imagine riding a wolf or a bear, looks ridiculous? You get my point, from this point onward the text is just obviously fake.
Everything up to this point seems to let the players get what they want: Ridable mounts. But I think even bethesda knows this is pretty unfeasible, let alone mounting a dragon.
Then horse armor get mentioned. Alright, horse armor. The thing that sparked so much controversy in Oblivion, they're gonna let you purchase it again. Yeah, sure.
Then a part about a questline "somewhere in morrowind". Okay, somewhere in Morrowind means they will either recreate an entire province again. Could be, but then the shapeshifting part renders it goofy again.
Last part about the thalmor: They again do what the players wanted: Getting rid of the Thalmor. It's pretty obvious that not someone from bethesda wrote this but just a casual forum-goer, judging by the poor quality of the text.
Thought so.