There are plenty of reasons why it was such a popular franchise in the first place, and why people got so attached to the original games. If the film really does get produced, and the producers manage to capture that original nostalgic feeling that drew so many people in the first place, this could be a complete blockbuster.
On the other hand, this should definitely not be a film produced for the sake of it. If a movie gets made based on “Zelda”, it should be a very carefully developed production with a lot of value to the fans. Otherwise, the effects could be disastrous for the franchise as a whole.
It would be bad enough if the film tanks, but if it drags down the entire franchise with it, that could be really bad for the future of the “Zelda” games.
Especially now, when fans have recently been annoyed about the apparent lack of progress on the new game, it’s very important for the people running the franchise to show their fans that they really still care and that they are willing to expand the franchise in meaningful ways, instead of treating it like a cash grab. It would certainly be bad to see “Zelda” go down the latter way, but so far we have no reason to think that at all.