Yay! Kill it, Discord! Kill it!
As you can see, I hate princess Twilight Sparkle. Don't hate on me because I hate on a cartoon character XD
If he did, then Equestria would have already been his. (I understand that something like that doesn't sounds like him, but lets face it, Discords episode came before the time travel episode.)
And he WAS trapped as a statue for all that time, i guess he just didn't think so much about the seeds when nothing happened when he came out. It's like a joke that no one understands until many weeks or months later (in Discords case, thousands of years), it's just not funny anymore. And now that the tree of harmony has it's elements back, then i don't think Discord can even touch it. AND, if one of the main six died, remember that Celestia and Luna can still use the elements.