We don't know what they're actually doing to the park. Looks to me like it's just getting a wider path, and I would guess maybe some kind of railing on the upper walkway. They're not removing it, just biggening it.
I seriously doubt this becomes amphitheater seating - or seating of any kind for that matter. Just a larger space with a few less trees in the middle. They're leaving all the larger trees at the back, so it'll still be nice and shady.