1) This sure feels like another one of these.
2) But part of Blizzard's more aggressive release schedule has been them reusing more and more content in the point releases. Seeing that only two new zones are brand new seems par for the course.
(Actually, how do the revamps work? Is literally half the initial expansion phases of existing zones? Or are they flat out replacing the zones (and presumably kicking newbie Belfs over to Org) a la Cataclysm?)
None of Midnight's zones are recycled, except in the lore. Old Silvermoon and Quel'thalas zones (Eversong Woods, Ghostlands, Sunstrider Isle/Silvermoon City) all remain in the game, available to starting Blood Elves and throughout leveling for all races, but the restriction from TBC back when they were implemented remain, you cannot fly there, and can only access it through the clunky portal in the Eastern Plaguelands or a teleport if you're Horde.
However, once you're at the appropriate level to do the Midnight campaign, you can access the entirely revamped Quel'thalas zone which encompasses all of the previous Quel'thalas zones, fully remade with the lore updated to reflect the healing of the Dead Scar and the destruction of Deatholme, with flight available, and a rebuilt, much larger and entirely new Silvermoon City.
It's similar to what they did with Arathi Highlands, where the old zones remains in the game but they made a completely revamped / modern graphics version with new lore and new rares / encounters back in BFA, but you can access both versions by just speaking with a bronze dragon NPC. For Midnight's two "recycled" zones, it's just on a much larger scale and the changes are a lot bigger, where Arathi was just basically upgraded graphics but very similar layout.
Zul'Aman raid instance in old Eversong Woods also remains available, but Zul'Aman as a zone for Midnight is entirely new content. The two other zones are brand new in the lore, since we only recently discovered the Harandir in TWW, and the Voidstorm just wasn't there before the Void invasion obviously.