The untitled Walker, Texas Ranger film is a sequel to Walker, Texas Ranger: Trial by Fire. It will release sometime in 2017.
CBS has announced that Chuck Norris, Clarence Gilyard, Sheree J. Wilson, Judson Mills, and Nia Peeples will be reprising their roles.
The only difference about Gilyard, is that he will ACTUALLY HAVE A ROLE IN THE MOVIE.
Not much of the synopsis is known, except it will be taking place right after the ending of Trial by Fire.
Sydney Cooke will return in the movie, since no one cared for Ranger Kay Austin. (I wish that Korean dude killed Kay Austin. If anyone deserves to be added to the Walker Body Count, it's her.)
Ranger James Trivette will also return, and actually have a role in the story, unlike in Trial by Fire.
I'm actually just joking. There is no sequel to Trial by Fire coming out soon. Guess we'll never know what happened to Alex. :)