Well, now that the Holy Knights are subdued, the demonized giants are slowly returning back to normal, but Imu himself has arrived, I feel pretty comfortable saying we're in the climax of the arc, especially remembering Oda saying he was planning on Lodestar next, at the Fiesta.
With Imu already coughing up blood the moment he arrived, and the proverbial smoking gun of the Pentagram he arrived from (which we know from Egghead, if the summoning is disrupted, they instantly vanish), I feel pretty confident in saying we're probably looking of a maximum of 10 chapters before Imu returns back, one way or another, then a wrap-up.
All in all, I'd say....November, give or take, as the maximum for everything being finished, and then they're off for Lodestar.
