Can I make feature requests?
The Feedback and Sugguestions forum is here for any and all feature requests that you may have.

When can I tell when a feature is going to be added?
As features are added, or bugs are fixed, they are amended to the latest changelog in the ChangeLog Forum

Is there any sort of modification or design community for the UBB?
Yes, UBBDev (ThreadsDev) is a long lived UBB development site geared towards support, addons, modifications, styles, etc.