I registered just to comment in this thread, even if it's a bit old.
I believe the first time I saw this was on DeviantART, by a person working for the show... Now, I can't seem to find that post for the life of me, seeing as I watch way too many people, but I think that Reddit post might just be a screenshot of the journal.. Curse my poor memory
Also, a lot of things point out to this actually happening, so I wouldn't brush it off until it's officially announced that it will/won't happen. As much as I want this to be fake, I do think the show has lost any creativity by this point and they probably think that alicorn Twi will probably "push" the things a bit. Happiness for the little fans of the show...and rage for many bronies.
I really don't support this idea. I see Twilight turning into a Mary Sue character. Not to mention I can't imagine how the rest of the girls fit into this whole scenario. A princess will have many things to learn and have no free time to spend with friends. And even though this kind of gives something to work over (Twilight trying to be a princess and still spend time with the gang) if there is barely anything about the rest of the cast, then I am SO done with this show! Twilight's not even one of my fave ponies. If I want to watch Twilight only, I'll go watch the sparkly vampires and then bleach my eyes or something..