I would venture to say that they have something very large in the works. I checked out their team page and they have quite a few employees. They have been funded and are also looking for new hires.

http://www.dropbox.com/about

Regardless, when you purchase something you are buying its current iteration, not something that you hope for it to one day be. This was alluded to in the comments of the original article and I thought it was worth repeating.