On one hand, there will always be a need for fruits and veggies; demand for the PRODUCT will be there. The million dollar question, however, is "…at what price?" On the other hand, given how dramatically the medical field changes what they define as healthy eating, it wouldn't be all that surprising if we are all eating only chocolate bars and Big Macs in 20 years. (In reality, just about every ingredient in even these two types of junk food comes from a farm somewhere though....) If you are a good businessman and know your stuff, you should be all right, but with lower prices for agricultural goods, you'll have to paddle hard to keep your head above water and avoid going bankrupt or being bought up by a larger farm. That Old MacDonald guy is a shark. The swallowing up of small farms by bigger ones is happening more often these days, as farming mega-corporations have the money and power to reign supreme over the family farms of yore.
Some things will be outside your control. For example, if you're a wheat farmer, one of your biggest competitors internationally will be China. Bad things happen to good people all the time. The brightly lit train in the tunnel coming at you called The China Express will be visible for a long time as they would grow crops at scale over a decade or more. But the storms that Mr. Weatherman didn't tell you about will just hit ya—and it is usually in those cataclysms that small farms evaporate.
One last thing to consider is that, because our government recognizes how important it is that we keep our farmers in business, there is an agricultural subsidy that provides billions of dollars a year to farmers. (Note: This fact does not mean that billions of dollars a year go to each farmer.) The money is designed to stabilize an industry the government believes is vital to our survival and that we can not be entirely dependent on foreign cashews. So they've got your back, kinda. They're still going to tax you though. And lots of little favors happen—at least for now—like free-ish water. While the country considers farming and in particular, the little farmer, Uncle Sam is lookin' out fer ya at least in some form. Just hope he still cares in a decade.