Your initial post asked what the response would be if scientists managed to demonstrate the emergence of life. I pointed out that a recent WT brochure answers this question.
Think of the challenge facing researchers who feel that life arose by chance. They have found some amino acids that also appear in living cells. In their laboratories, they have, by means of carefully designed and directed experiments, manufactured other more complex molecules. Ultimately, they hope to build all the parts needed to construct a “simple” cell. Their situation could be likened to that of a scientist who takes naturally occurring elements; transforms them into steel, plastic, silicone, and wire; and constructs a robot. He then programs the robot to be able to build copies of itself. By doing so, what will he prove? At best, that an intelligent entity can create an impressive machine.
Similarly, if scientists ever did construct a cell, they would accomplish something truly amazing—but would they prove that the cell could be made by accident? If anything, they would prove the very opposite, would they not?
The same brochure also states the "life from life" principle. And they argue on the next page that such a scenario would demonstrate their point.
If the chemicals in the experiment represent the earth’s early environment and the molecules produced represent the building blocks of life, whom or what does the scientist who performed the experiment represent? Does he or she represent blind chance or an intelligent entity?
What the WT objects to is the idea that life could arise by its own by "chance". Scientists creating life in a laboratory would not meet this test in their view. The contrast is between an "intelligent entity" creating life and it arising by accident or by "chance".
All scientific evidence to date indicates that life can come only from previously existing life. To believd that even a “simple” living cell arose by chance from nonliving chemicals requires a huge leap of faith.
https://download-a.akamaihd.net/files/media_books/d0/lf_E.pdf