Dave, there's a whole lot of answer to that little question.
Quick answer, figure 1 lb of hops/bbl and a single plant at full maturity should yield 1 to 2 lbs of dried hops, depending on variety. An acre can hold 900 to 1200 plants, typically. So you can do the math from there based on how much production your local micro is brewing.
The reality is that they rarely sole source hop or malt purchase and quality of the product is usually a higher concern. Some will demand pellets instead of whole cone. Many will want testing performed to give them the alphas, etc.
Then there's the simple question of what variety can you grow vs. what they want to buy.