(1 & 2) These don't work because there simply ISN'T a 7th Element of Harmony. You're basically retconning the main plot point of the series if you do that.
(3) Derpy will NEVER get her own episode. Not after all this controversy. Plus, a speechless episode? Really? Older fans could appreciate the art in that, but this is a kid's show, and they'd just be confused and complain. They'd also complain on the focus of a background character. Bronies would love it, but the target audience would hate it with a passion.
(4) Nightmare Night was a one-time event, I would think. In the same sense that we never saw Winter Wrap Up in Season Two. Plus this would make Trollestia canon, which the creators won't do.
(5) Lyra and Bon Bon's relationship is fanmade, and probably won't be canonized. Plus you still have the background-focus thing that little kids would hate. Also, the LGBT debate is too sensitive to put in a kid's show right now (which is stupid, as it seems so obvious to give equal rights, but that's beside the point). I doubt that we'll see a reference to the Royal Wedding episode, since most episodes tend to be self-contained. Finally, the synopsis is too spoilery. Most synopses won't do that.
(6) Scootaloo CAN fly, we've seen her do it on occasion. It just doesn't last very long, and she only hovers, not really going in any direction other than up and down. Most obvious example is during the "cheering up Apple Bloom" part of The Cutie Pox. It's just the bronies that believe she can't fly, so this episode won't work.
(7) Death? Really? In a kid's show? No. Plus, the rock farm may not even exist, seeing as how Pinkie ended her story with "And that's how Equestria was made."

Overall, the "leak" is fake, for the reasons stated above and because it's too soon for such a thing to occur. Not to mention the fact that this is WIKIPEDIA of all places, which is known for being edited with random crap, since they have an "anyone can edit" philosophy.