Promo image courtesy of Alafista
From the article:
According to the Japanese Moon Phase message board, the advertising "obi" on the freshly released Japanese Trigun Maximum volume 14 manga includes a confirmation that "Trigun the Movie," an original story motion picture promising "Vash vs Wolfwood!?" will hit Japanese theaters next year. The movie will be animated by Madhouse, directed by Trigun television series director Satoshi Nishimura, and written by Yasuko Kobayashi, the screenwriter of the Gilgamesh and Guyver TV series.