I'm not really expecting A Face in the Crowd, Throttle or In the Tall Grass to be in the collection, if only because he wrote them with a collaborator. I sort of expect the two with Joe Hill to be published separately in another book of four novellas. Maybe they'll do two more together or each write one by themselves to go along with the collaborations. I could definitely see something like that happening.
As for the poems and essays, if I had my way I'd say poems yes, essays no. As great as it was I never felt that the baseball essay really fit in with the rest of Nightmares and Dreamscapes. Besides, I think that with the various essays and non-fiction pieces he's done for magazines and newspapers over the years, the Pop of King column, and his recent Kindle release "Guns," etc. there would certainly be enough to warrant a collection of a 20-30 of his best non-fiction pieces. Looking at the essays section here on his official site I see several unpublished or uncollected ones that I'd be quite interested in reading.
With that said, I did think that the inclusion of the teleplay "Sorry, Right Number" in the same book actually worked very well and I wonder if he would consider doing the same for the episode of Under the Dome that he wrote? I think that would be a nice bonus for fans of the show. The problem is that, unlike "Sorry, Right Number," it isn't a standalone episode and would require a certain degree of familiarity with the show. Still, if it was placed at the end it could easily be skipped by those who aren't interested. Personally I'd love to read it and compare the script to the episode itself.
But based on the recent stories I have read, this next collection will be another winner regardless of what makes the cut.