If DR Luffy happens, it was a weird choice to have him stay behind and face Imu later. I feel like Oda needed an excuse to raise the stakes and make a difficult situation arise without Luffy in the picture. But yeah, DR Luffy is a possibility regardless.
I wouldn't discard the possibility of Loki being the one getting DRed, with Luffy having to take him down despite his injuries, which would put him in a morally challenging situation.