sigh*... I know logic is hard, but try.
First, they don't say that scientist may succeed one day. They say "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?"
That does not in any way say "may", it says "if". It's similar to saying "Humans will never be able to shoot laser beams from their eyes, but if they could, that would be terrible." The latter hypothetical doesn't negate the former.
How do we know that "if" and "may" are different? Try replacing them in a sentence. "If you go outside, then you will be cold" doesn't make sense as "May you go outside, then you will be cold". Similarly, "you can go to the movies if you finish your homework" doesn't make sense as "you can go to the movies may you finish your homework".
The hypothetical "if" (not may) does not negate their teaching that God is the only source of life.
Evidence is so inconvenient.
LIFE COMES ONLY FROM LIFE. “With you [God] is the source of life.”—Psalm 36:9.
https://www.jw.org/en/publications/magazines/g201501/origin-of-life/
PROTIP: If you are going to link to a doc to prove your point, actually know what it says and what the words mean.
Okay, well that's embarrassing.
Until this exchange I had a vague impression of someone who was arrogant but intelligent. Now I realise only one of those.