My speculation is that Friday 9/7 and Saturday 9/8 will be Night of Joy dates, but I don’t think they have been officially announced yet so big caveat there.
The Thursday 9/6 and Sunday 9/9 dates will in all likelihood be MNSSHP dates. MNSSHP has been on the Thursday and Sunday surrounding NOJ the last two years.
NOJ used to be a hard ticket event at the MK where it would close early that Friday and Saturday night. They did NOT do this in 2016 and 2017, instead all the events were held at WWoS.
So my speculation is….
1) Friday 9/7 and Saturday 9/8 will be NOJ nights and perhaps they are moving back to making it a MK ticketed event.
2) Those dates could just be a random placeholder by Disney that will get adjusted later (has certainly happened before).
3) Thursday 9/6 and Sunday 9/9 will be MNSSHP nights. (High degree of certainty here)
Hope that helps!