NextD N1 currently doesn't have a plan to upgrade to Android 5.0+. Other than KODI, most Android apps do not require Android 5.0+. Regarding KODI, v16.1 should run perfectly on NextD N1 with no problem. Please note that KODI v17 is reportedly breaking a lot of 3rd party add-ons as you can see from many user reviews.
We are working on the next generation product NextD N2, which will be based on Android 7.1.