Amazon isn't likely to meet many competitors because they're not profitable. You look at their model and go "wow, that's a lot of money to spend in order to break even in 20 years."

85% of the world's hazelnuts are grown in two counties in Oregon. That hasn't changed since WWII. The reason is that a hazelnut tree is a useful producer for about 30 years… and at current and historic prices, the break-even point for commercial hazelnut production is 18 years. So nobody plants them. If it's going to take eighteen years for you to recoup your investment and barely a decade of profitability before you're back in it, you're going to find something else to plant.

I think what's far more likely to happen is for shipping to get more expensive, local goods to improve their edge and the global hegemony of internationally-sourced goods to decrease. It isn't a feel-good farmer's market thing by my reckoning, it's a "leather goods made in Los Angeles that cost $8 extra to make are suddenly price-competitive when shipping leather goods from Vietnam costs $8."