If not a sequel, I would simply want to know how much time Ben and Mark spent there after the novel ended. Or if they did not accomplish their goal completely.
I will have to wait to see if that is addressed in The Dark Tower (I dared not click on those spoilers).
I loved this short story (I read it this morning as I came to my work). I already knew there were two Lot-related stories in this book, and I even knew this was the name of one of them, but I had forgotten it (I always try to forget any spoilers to stories I have not read and then try to remember as much as I can from stories I have).
It was a pleasant surprise to see the characters' reaction when they realized where the car had been left. And to learn more about how the surrounding towns have dealt with this infestation. (We only saw part of it in the novel, and from someone else's point of view, and from newspapers.)
As a side note, with so many people saying how the first Dark Tower book is hard to get into, it was nice to see I liked it just fine when I read it. Since I really enjoy "quest" stories, I am used to the way those start (slow, perhaps, and with few characters) and then build up as they go (explore the world, get more characters into the questing party, reveal the characters' goals and motivations). Of course, things exploded even more in the following books, and those are the ones that completely hook you if you are not already convinced.