Where I do find feature lists for upcoming Ubuntu versions? [16.04]
Wikipedia seems to have a rather extensive list of features, including the addition of Unity 8, and the possible transfer from Python 2 to Python 3. It probably isn't a very good idea to start preparing, however, as April is still 4 months away, and a lot could change in that time.
https://en.wikipedia.org/wiki/List_of_Ubuntu_releases#Ubuntu_16.04_LTS_.28Xenial_Xerus.29