"It's over. There's not going to be another one," Sirtis told the crowd flatly in reponse to a question. She claimed it's due to the box office drubbing endured by Star Trek: Nemesis.
Sirtis, a self-proclaimed fan of Nemesis, said the film would have done "blockbuster business" had Paramount released it in February 2003 rather than "five days before Lord of the Rings" in late 2002. She then suggested it's time perhaps for Star Trek to retire for at least a decade before it's brought back.
Marina Sirtis is not the first TNG cast member to proclaim the franchise (at least with the Next Gen cast) dead. Patrick Stewart and Jonathan Frakes have both said as much.