Maillol does not complain about impossibilities or his own incapacity. He simply reports what he can.
If Keltham returns to a state where he is not - actively determining whether to leave Cheliax, especially for Osirion, through planned deeds that have not yet been performed and resolved themselves - if Keltham is not holding concrete plans to decide about that matter the next day, at a particular time, or if he's made whatever decisions he intends to make and become again Cheliax's guest - then, Maillol thinks, they would no longer be in the ambiguous fringes of Asmodeus's command.
It is not clear to Maillol that they have been definitely commanded not to statue Keltham now, for just a year, while Keltham hasn't yet made a decision to depart but has decided to make a decision about it...?