Following the recent postponement, the official support for the MyBB 1.6 series has ended as of 1st October 2015.
The 1.6 Support forums have been archived and we will no longer provide assistance regarding the 1.6 series (that does not include the 1.8 upgrading process).
No further maintenance and security releases or updates will be provided for that branch.
We strongly recommend all users who still operate 1.6 boards to upgrade them as soon as possible. Detailed information on performing upgrades can be found in our upgrade instructions. The MyBB Team and the Community can provide further advice on our support forums.
MyBB Blog 
I remember being excited for 1.6 when it was getting ready to launch! Good times.
its very sad to hear abandon MYBB 1.6x…. because i believe most plugin is developed for support 1.6x version …. and 1.6x is more light than 1.8x ..
i hope MYBB 2 bridge in between
Actually there have been at lot of optimizations in MyBB 1.8 which makes 1.8 faster than 1.6. And there are already a lot of plugins and themes for MyBB 1.8.
MyBB 2.0 is whole new software so it’s rather unlikely to “bridge in between”.
But not as good as 1.6x let’s see how 2.0 goes!
That’s rubbish as may of us are still using 1.6 as the plugins are simply not available for 1.8