Yeah, it will be interesting to see how they handle the aftermath of the bombs going off. Realistically a good chunk of the cast was probably exposed to some pretty serious radiation, but I can't see them taking out that much of the cast unless they're ending the show.
Morgan and Grace, and Dwight and Sherry should be WD's by next Season but they probably still have plot armor. June and John's father despite being closer to the explosion are already in the bunker previously sourced as a shelter. Alicia's probably okay, and who knows about Strand? But also, everything around them should be irradiated at this point--any food or crops that they had been growing are toast. My guess is that they are going to have to fight to get in one of the established bunkers for supplies--and then head away from the blast zone.