He is most likely alive. Sukuna said Megumi was only in a suspended state of death and healed his injuries, though I'm unsure if Sukuna exorcising the shikigami automatically lets Megumi wake up (。•︿•。) But I'm pretty sure Sukuna won't let him die (´。• ᵕ •。`)
I've binged this in like one day and I'm on a rollercoaster of emotions rn? I don't even know who's dead or not :DD