The earliest that preproduction would begin would be in one year, Maxwell said.
During the filming of "Gods and Generals" in 2002, Maxwell said the only way "The Last Full Measure" would not be made was if he and Turner both died.
"I'm more than just interested as long as I'm standing," he reiterated Thursday.
It's how to get the movie made that is less clear, he said.
"Gods and Generals" made only $12.87 million at the box office during its 2003 release with a budget the Internet Movie Database says exceeded $56 million.
Strong DVD sales are helping to lessen the disappointing box office result, Maxwell said.
More than 1 million DVDs were sold as of Thursday, he said.
The future of "The Last Full Measure" is "largely contingent" on DVD sales, Maxwell said.
"If they continue to be strong then we will be back to a more sanguine feeling about moving forward," he said.
Maxwell is rewriting the script for the movie that features three new characters, U.S. Gens. Ulysses S. Grant, William T. Sherman and Philip H. Sheridan, along with characters from the first two films, U.S. Col. Joshua Chamberlain and Confederate Gens. Robert E. Lee and James Longstreet.
Maxwell said Robert Duvall has "emphatically" committed to reprising the role of Gen. Lee that he assumed in "Gods and Generals."
A large portion of "Gods and Generals" was filmed in Washington County.
The Washington County Commissioners and the City of Hagerstown helped Maxwell's Antietam Films in preproduction on "Gods and Generals" and offered a preproduction loan of $300,000 for "The Last Full Measure." The loan will become a grant if half of the movie is filmed in the county.
Maxwell said he intends to accept the offer.
"We want to do what we did last time," he said. "Just tell them to control the level of building so we have space to film."
"Gods and Generals" was an adaptation of Jeff Shaara's prequel by the same name to his father's bestseller, "Killer Angels."
"Killer Angels" was the basis for "Gettysburg," which starred Tom Berenger as Gen. Longstreet and Martin Sheen as Gen. Lee.
Jeff Daniels starred as Col. Chamberlain in both "Gods and Generals" and Maxwell's critically and financially successful "Gettysburg."
Critics nationwide panned "Gods and Generals."
Maxwell said he is busy filming a documentary on George Washington but is looking forward to coming back to the area.
"It was exciting last time," he said. "I hope it can be exciting again."