I assumed title drop in January and first trailer in April, like The Last Jedi.
Disney may have learned their lesson with marketing Solo while the Avengers is already dominating. Drop the teaser just before Endgame comes out and you can have it running before the other massive movie of this year.
As for the title, Endgame managed to hold out for an extended period and create plenty of hype so they coodbbe trying to replicate that.
Then actual marketing can start October, when there’s not much competition left besides Jumanji 3.