Curve25519-SHA256 is the default KEX in openSSH too now!
Since some hours curve25519-sha256@libssh.org is the default KEX in OpenSSH!
Several weeks ago Aris added a new Elliptic Curve algorithm for key exchange using Curve25519. After he wrote some kind of a RFC and implemented it in libssh he started to suggest a patch for OpenSSH which finally has been integrated.