There are an average of 163 posts per day, so we'll be at 10,000 by the end of the day on Thursday if the averages hold true - aren't you glad you are not receiving this as a mailing list!
Unfortunately, it doesn't appear that there is any way to verify which post will be number 10,000. It will all seem trivial as we hit 1,000,000 posts sometime in September 2021.