Disregard all you Californian people who are still on April 1st!
I am surprised to learn that the entire update is genuine. I knew that the second and third screenshot were real because they've been shown to us before. The thing with ghosts is even on the wiki. I knew that shield sprites were planned for 2.1, so it didn't come as much of a shock, but there was still the possibility that they're fake, what with Mystic's "they also just look awesome" comment. Glad to see they're aren't.
The Lua thing seemed rather unlikely but possible. I knew that JTE had been working on Lua before he was a dev, and I've heard some stray comments by a few devs that "something big" was coming. That's what it is. creator.wad appeared to be the obvious joke, because even with Lua you can't just change sector shapes. Here's the thing: You don't. The level consists of a grid of smaller sector and you can change their heights and flats. The Eggmobile player can shoot and use his dash as often as he likes, so he's really quite powerful.
The whole time I was thinking that the joke was mixing real updates with fake ones. Well played, dev team, you fooled me!