It [i]possibly[/i] could have, provided that everything went swimmingly for the Didact - winning the political battle over the Master Builder so he wouldn't be exiled to the Cryptum. It's implied that Precursor artefacts are perpetuated by the presence of the Flood, it got to the point where their very presence would distort time and space around them. Kill the Flood, lessen the effectiveness of the Precursor constructs - that's why the Promethean Knights could have been an effective idea if the Didact had sufficient numbers. If the Didact's star-hopping strategy was implemented, the Forerunners would have at least have actually been prepared for the Flood.