Hi!
You can always think positively, and expect to have many more reviews to respond to, and open a thread. Honestly, we don't mind even if it's for just one review. It can become a way to open a dialogue with your readers, and maybe spark some good discussion that can improve the story.
Alternatively, if you can keep the responses short, some of our authors do reply in an author's note at the end of the next chapter. I will point out that the danger here is in going over the 600 word per chapter limit we have for author's notes. I know a couple of authors who can do this successfully, but I've also had to ask a great many others to correct this very thing.
I myself have review reply threads for my stories, and since I do a good many oneshots, I have a general reply thread in Originals and in Games for those. I just note in each reply which story the review is for, and then reply to it.