Science will never be able to prove the existence of God. But science will most certainly be able to prove or disprove evolution.

If evolution is effectively disproved, then the only other alternative (albeit logical, abstract, philosophical, metaphysical, religious alternative) is that God spontaneously created it.

Just because an option is not a scientific one does not rule it out as an option. If its the only alternative idea, it makes no difference if it is a scientific alternative or a spiritual alternative. The only thing that is important is that it is the ONLY alternative.