On Dec 8, 2015 7:08 PM, "Wladimir J. van der Laan via bitcoin-dev" <bitcoin-dev@lists.linuxfoundation.org> wrote:
>   - Gregory linked to an implementation but as he mentions it is not completely
>     finished yet. ETA for a Segwit testnet is later this month, then you can test as well.

Testnet4 ?