Few days ago I got answer regarding to my email sent to Dropbox:
"Thanks for reaching out to us.
We receive a lot of requests for Dropbox clients for devices like the Blackberry Playbook. Unfortunately we don't have any plans to create a client for those devices at this time, however, we may decide to do so in the future if enough users express interest. The best place to make such a suggestion is Votebox - available at dropbox.com/votebox (you have to be logged in to access). You can check out and vote on other user suggestions and submit your own for others to vote on at that site.
In the meantime, if you want to access Dropbox on your mobile device, you can do so at m.dropbox.com.
Feel free to reach out to us with any additional questions/feedback.