The magic command
%matplotlib notebook
fails to create an interactive matplotlib window within the notebook with matplotlib2 beta (matplotlib-2.0.0b4+2344.g7b27a1b) and matplotlib2 rc (2.0.0rc2+2827.gab98852)

Here is an example
https://github.com/fedhere/notebookTests/blob/master/mplnotebook_test.ipynb
The first cell does not show a plot inline nor it generates a popup window.

Tested on python 2.7.12 and python 3.5.2, ipython 5.1.0, jupyter 4.2.1, Chrome 55, macosx-10.6

Switching back to matplotlib1.5 everything works fine (tested on pyton3.5.2)