There were many American slave revolts prior to Turner's.
1712 New York Slave Revolt
1739 Stono Rebellion South Carolina
1741 New York Conspiracy
1800 Gabriel Prosser
1805 Chatham Manor
1811 German Coast Louisiana
1815 George Boxley, Virginia
1822 Denmark Vesey, South Carolina
1831 Nat Turner's rebellion
And one after, at sea.
The makes questionable the effect one revolt had on Southern manumission and laws taking freedoms from free blacks that were put into place in the mid-1830s. It had some bearing, but in Virginia where the revolt occured, it had little effect on manumission- which continued until 1865. I don't believe Turner's Revolt was not the sole cause to the change of attitude across the South started in that decade. The tougher laws and changes came in the 1840s, 50s, and 60s.