To be fair, no-one is assuming anything. People are stating quite logically that it would be much easier to do it now while the team who did TNG are still warming chairs. At this point, they are basically extending a current project. In the future, they would be starting a whole new one. Here is an interesting question, was the original film for DS9 and VGR stored as diligently as that for TNG? Is it all still kicking around in a salt mine?