No. Nighthold will start next year. There was a quote stating that already iirc. They have this thing called a 2 week christmas break plus a thanksgiving break, it's unlikely they'll release nighthold between the two.
Plus, 3 raids in 3 months? That sounds like another xpac that had a huge content drought because of badly placed raids...called...Mists of pandaria.
They will not make that stupid ass mistake with releasing all the raids in 3 months. Fricken nightmare won't be out til the end of September for fucks sake and you want Nighthold 2 months later?
You REALLY must want a 14 month xpac gap.
Nightmare N/H 9-20-16, M 9-27-16
7.1 probably early November/right after blizzcon.
Nighthold in January.
7.2 in May/June (at which point we will, if we have done everything every day finally have maxed artifact weapons in March/April)
Honestly the stupidity of the post above mine is actually driving me insane, I hope they're trolling.