I think the DIS posted an article last week saying they found something that suggested work to be done in the lagoon, but nothing as specific as this. I think WDWNT is playing it safe with the new show before 2021 though. As other people have said, this show can debut as early as this year and next year. There's another reason why I think that this might be true, but I really can't say it because I don't have it confirmed (and probably couldn't say it anyways due to the person giving me the info is a CM). I'll just say that Illuminations can really be going sooner rather than later.
So, in my loudest Luke Skywalker impression... "NO!!!!!!"