I suppose I'm thinking of franchise as a wider term, including the way geobra are partnering their own cartoons with their own products - Super 4, the Movie, Dino Rise, &c. But you're right, Graham, it's really a term for a borrowed business model.
I agree: I'm sure they are targetting collectors in their 40s and 50s. Spirit is a noughties thing, but the rest all seem to have been big in the 80s - as Star Trek would be if that does come out (think the movies here). Lego have sown up all the big selling contemporary franchises: MCU, Star Wars, Harry Potter, Jurassic Park, LOTR. Bond's been big in every decade. Beyond that they have to think about the audience - Fast and Furious for kids?
Perhaps this post should now turn towards eighties movies/TV series that could be turned into themes: Gremlins? Flash Gordon? Mad Max? Alien? They've missed the boat on Indiana Jones!
Of course, I wouldn't want any of these ...