At the moment inorganic nitrogenous fertilizers are cheap. They are derived from the methane in natural gas by the Haber-Bosch process, so the price of fertilizers is tied to natural gas supply. Estimates vary, but we probably only have about 60 years of natural gas supply left when you factor in the increasing use and near-peak production (according to the 2013 International Energy Outlook [1]). And the extraction methods are becoming more environmentally challenging: fracking and shale gas are the natural gas sources of the future. The food-price effects of that will be felt as soon as we pass peak gas production. So we need a new way of fixing nitrogen in the near future.
Secondly, while much famine is caused by war, there are many other causes, and hunger is more widespread than famine. Increasing world population, especially in poorer areas, and a complete failure to make any progress so far in fixing the inequality-related causes of hunger mean technological crop solutions are likely to be important in feeding the future population.