The dryer conditions you speak of aren't really showing through to production data in the US, at this stage. The last several years have shown relatively consistent yields and I haven't noticed any long term trends towards reduced yields.
Also worth remembering that the science of agronomy is extremely robust and much faster moving than other types of biomedical and pharmaceutical research. I'm always amazed how many new seed varieties are coming to market with specifically bred traits, such as drought and disease resistance, early vigour etc. I think science will continue to play a major part in world production, as population increase.
