Poverty is falling dramatically right now, and is falling faster than the UN ever predicted. It is quite likely that we can feed 7bn people.
We have 80 years to come up with the technology to feed another 4bn by 2100. And population will probably fall after that. That sounds doable to me. Food technology is making huge gains, if we have lab grown meat at almost a tenth of the cost, imagine how much easier it becomes to feed everyone.
Why the pessimism? I know everyone's facebook feed is full of the world ending, but the situation isn't actually that bad.