RCCL has always said that some stuff won't be done until December - but that is more the cabanas and beach areas from what I understand. They are still saying the water park is on schedule for opening in a couple weeks. Which seems very ambitious based on the last picture I saw posted (Matt Yee on Facebook posted a pic not too long ago...he's a performer on Anthem. It still looked like there was a good amount to finish on the water slide, and then the ground areas still need to be landscaped/finished).
ETA: my cruise is in 26 days and they are still selling the zip line, water park access, balloon ride, etc. So they are still maintaining that it will be open when I go. Fingers crossed they can make it happen!