Was this an important issue w/slavery? If the British won the war were African Americans more likely to gain, or was this merely a war move and probably dismissed later?
At various stages during the southern campaigns the British did offer freedom to slaves who joined them in the fight against the revolution. There was though no plans at the time for a widespread freeing of slaves by the British, and in fact the British did not begin to end slavery in their empire until the time of the napoleonic wars.
With that said, of the British won and the USA stayed in the empire, slavery could have potentially been abolished sooner than it was, as the Brits had ended it well before the American civil war.
Yes. in 1775 very early on in the war Lord Dunmore, the Royal Governor of Virginia holed up in Norfolk, issued "Dunmore's Proclamation"
He promised the slaves of Patriots freedom if they would leave their masters and take up arms against them. He had some success and some free black and runaway units were founded by the British, but they were not very notable and used mostly in labor duties.