The Shubert makes sense. Following himself in it is probably the only way he knows he'll have a theatre a year in advance. Now, when does Mockingbird close: Daniels has said he's in it for a year. For an actor of his stature, that could mean October (start of rehearsals), December (opening) or sometime in between. If they choose to replace him (Reed Birney??), it could run til July 2020, since Music Man starts previews September 9.
The other option is The Broadway, where the original run of Music Man concluded its run, and where they could sell 250 more seats a night. But depending on when KONG closes, it wouldn't have a proper tenant for a year+.
West Side is also a factor: There were rumors that Rudin wanted the Winter Garden (where it played originally). If not that, then The Broadway or Imperial would be logical backups.