Wano and the reverie are SUPPOSED to take place this year so its more than likely not gonna be that much longer. maybe like 30 more chapters at most. Wether or not Oda can still to his schedule is unknown tho.
I didn't really think about that Nova that is true but I don't really see Oda flipping around in the middle of the arc. Maybe after the main events are over and Luffy is just sailing oe hanging out like in dressrosa or post EL