If by this they mean conclusive scientific evidence, I don't think they will ever be persuaded. I don't think God would allow it, for one thing. Faith is an essenital component of all religions, and faith can't exist unless there is also the possibility to doubt

In the days of the bible there were miracles galore. A lot of those people certainly didn't need faith to believe, what with the parting of the red sea and all.
So, what's changed?