https://4.nabox.org/downloads/
If you guys feel adventurous, you can test today the future of NAbox 😄
v4 is the path forward and no features will be delivered in 3, as far as I know, v4 has feature parity with 3 at this point (and some more)
Migration from 3 to 4 is available if you installed a recent version of 3.5.2 (yes, there has been a couple of iteration for that version number)