Sorry, there is slight confusion here...probably based on the similarities to the names. But The San Angel Inn (inside the Mexico pavillion) is not being currently changed and nothing new there - they've been taking reservations all along for the San Angel Inn so what OP got was reservations at the same-old-same-old restaurant in Mexico (not to say that's a bad thing...we love the San Angel Inn!)
It's the outside restaurant - that was just a counter service - that is currently closed and being rebuilt as a combined new counter service & table service. It will be called La Cantina de San Angel (counter service), and a new table service in the same building out there called La Hacienda de San Angel. The San Angel Inn remains inside in the Mexico pavillion marketplace area.
They are not yet taking resrvations for La Hacienda.