No. There have been a bunch of "leaks"/"dumps" claiming to be from Dropbox posted on pastebin for the last two years or so. Most are just rehashed from other pw dumps.
Troy hunt: https://twitter.com/troyhunt/status/599150465335431169
And this latest FUD came from leakedsource.com, who published a list that was claiming to be Dropbox usernames and hashes, but if they did their due diligence they would have notice that the list was in fact Tumblr. They issued a correction later: