Well there is a couple of things you can do, you can wait and let it come all the way down, or you can go ahead and replace it now. That is the way the headliner starts to fall, a bubble here or a small sag there, but where ever it starts - it's on the way down. You will need the correct amount of headliner material and high-heat headliner grade adhesive like the Max Professional headliner adhesive or the 3M 76 High Tack spray adhesives.
The grand or large minivan headlienr kit will work for the large Voyager minivan.