There has been an internal announcement, and yes, concept art has found its way to employees. I highly doubt that will be shared with the public though, less an announcement. The plaza isn't "top secret" or anything though.
The metal structures should be telling, but that isn't all. Yes, there's more and I honestly can't tell you when it will open up. I'm going to guess that they're gunning for before Curious George closes so they can take advantage of the water play area during warm September weekends.
No grassy areas at all, I think. And it won't make HHN this year (at least in time for a maze)... or probably ever. Grinchmas is still in the cards.