What were the british planning with regards to slaves once they won the american revolution?

Only 50 years after the defeat of the British at Yorktown, most Americans had already forgotten the extensive role black people had played on both sides during the War for Independence. At the 1876 Centennial Celebration of the Revolution in Philadelphia, not a single speaker acknowledged the contributions of African Americans in establishing the nation. Yet by 1783, thousands of black Americans had become involved in the war. Many were active participants, some won their freedom and others were victims, but throughout the struggle blacks refused to be mere bystanders and gave their loyalty to the side that seemed to offer the best prospect for freedom.

The answer is crop yield.