Real talk, HAS to be some random shit like a slave revolt or something like that. Whoever the hell is attacking the Holy Land is about to be wrecked by Imu as a hypetool.
And even as somebody who thinks Imu will be FV and God tier, Oda would not waste Blackbeard or Dragon and potentially even off-screen their death/defeat at the hands of Imu.
Unless he takes a break from Elbaf fro a couple months to properly show the burning and aftermath? No shot it is either Teach or Dragon.