Manga ending 2015 or 2016 , next year is too soon , there is still SO MUCH that kishi needs to sourt out , have a timeskip to set the scene for naruto vs sasuke , which then requires a re-introduction for EVERYONE which will probably require a few more story arcs and more fights to show newly attained powers of the main characters.
so i estimate 800 chapters is about right
one piece will get over 1k so that doesnt really matter