As far as I can tell, it is not supposed to be down for any extended time and they are not doing Ghost Galaxy this year. Under the refurb notice, it says that it will be down August 26, 28 and September 19. You should be good on the 29th. I have not seen them say when they would change it from Hyperspace; speculation is that it stays up until Rise of the Resistance or longer.
But I am not “in the know.” One site said it was down to do the overlay but then other places say they weren’t doing it. I guess we will see tomorrow? Back in July, it was widely reported that Hyperspace would be up through the Halloween season.