on the last bi-weekly developer meeting, we've decided to 1.) start a beta-test period for the new gnrc network stack and 2.) remove the old network stack from our master tree.
ad 1.) The new network stack, also known as generic or gnrc stack, is intended to become the default network (IPv6) stack for RIOT within the next couple of weeks. Thanks to the tremendous work of the NSTF (network stack task force) the stack has finally reached a state where you can run a full IP stack (from UDP down to PHY) as well on native (Ethernet and plain IPv6) as on real (802.15.4 capable) hardware (6LoWPAN).
In order to converge to a stable state as fast as we can, help for testing, finding and fixing bugs is highly appreciated.
We would like to invite the whole RIOT community to check out the current master and play around with gnrc features as a kind of beta testing.
ad 2.) Since the gnrc stack is meant to replace the current IPv6 stack, we've decided to remove this stack already now. For a summary of pro/con arguments please check the meeting minutes. 
One week from now (Wed 05.08.), we will tag the last commit that contains the old network stack, and then merge a removal PR (probably #3334 ).
Issue #3417  will be used to track removed functionality.
If you have important arguments against removing the old stack, speak up!
Kaspar and Oleg
 http://riot.pad.spline.de/15  https://github.com/RIOT-OS/RIOT/pull/3334  https://github.com/RIOT-OS/RIOT/issues/3417