The series would have lasted for seven seasons whatsoever. Voyager's ratings weren't that low that it would have justified a cancellation of the show.
There were never any serious discussions about cancelling the show either. The only thing that did seem to worry those in charge was that neither Voyager nor DS9 had the same high ratings as TNG.
Not to mention that their rantings about "Seven saved the show" isn't exactly the truth either. The ratings were lower for seasons 4-7 than they were for seasons 1-3.