The earth is not a perfect ball, and it is not simply floating in space: It is spinning on its axis, and revolving around the Sun: In case you don’t know.
But if you are wondering when people will stop believing in this and accept the Flat-Earth thesis, I will simply say:
Maybe before December 31, 3000.
That’s because I am an optimist.
If this doesn’t happen by then, there is little hope this will ever happen, until there is a powerful theocratic dictator who gets full command over people’s thinking and tells people what to believe.