An OVA of Spice and Wolf II was announced to be released on April 30th before the airing of the second season. It's called episode 0 and will be bundled with Dengeki Visual Novel "Spice and Wolf: Ohkami to Kin no Mugiho". The episode 0 will not be aired on TV.

Spice and Wolf II OVA "Chapter 0: Ohkami to Kohakuiro no Yuuutsu (Wolf and Amber-colored Melancholy)"
Duration: 24min

"Ohkami to Kohakuiro no Yuuutsu" is originally a short episode in the volume 7 of the novel.

Source: Scan of Dengeki Maoh

Edited on Feb 5th========================
Spice and Wolf II will be aired this summer.

Staff
Director: Takahashi Takeo ("Spice and Wolf")
Script: Arakawa Naruhisa ("Spice and Wolf", "Elemental Gelade")
Character Designer&Graphic Art Director: Kobayashi Toshimitsu ("Futakoi Alternative", "Vampire Knight")
Production Studio: Brains Base

Source: Scan of Dengeki no Kanzume