Hey everyone, this is just speculation from me no facts or anything like that so here we goes:
Patch 9.0
Castle Nathria: it will be the Uldir of this expansion.
Patch 9.1
Sylvanas raid: will be the equivalent to Jaina's raid was in BfA.
Patch 9.2 Mueh'zala's raid: Usually the biggest mid raid in expansions Bwosamdi and Talanji will get involved there.
Patch 9.3 The Jailer's raid: the last official raid of the expansion and the Jailer will be the last boss of it.