That "probably" is doing a lot of heavy lifting. That said, whether they sell it or not, it's all that data that is their primary value store at the moment. They will either go public or sell, eventually. If they go public, it'll likely be similar to Dropbox; a single fairly successful product, but failing attempts to diversify.
"Selling" is a load-bearing word, too. They're probably not literally selling SQL dumps for hard cash. But there are many ways of indirectly selling data, that are almost equivalent to trading database dumps, but indirect enough that the company can say they're not selling data, and be technically correct.
