De Jornada nas Estrelas: A Próxima Geração - Cancelamento :
Although the cast members were contracted for eight seasons, Paramount ended The Next Generation after seven, an unusual decision for a successful television show. Although doing so let the studio begin making films using the cast, the main reason was that additional seasons would likely have reduced the show's profitability, due to higher cast salaries and a lower price per episode when sold for stripping. The cancellation also encouraged viewers to watch Star Trek: Deep Space Nine and the forthcoming Star Trek: Voyager, both of which were much cheaper to make than The Next Generation. The show's strong ratings continued to the end; the series finale was ranked #2 among all shows that week, between fellow hits Home Improvement and Seinfeld.
Essa explicação parece bastante lógica para mim. Cancele esse show de alto custo para que os fãs desejem filmes e programas mais recentes, o que, por sua vez, terá uma margem de lucro maior, além de impulsionar a franquia.