At a recent meeting, one of our state extension specialists gave a presentation on nodulation. He made the comment that these bacteria can live in the soil up to 5 years.  So, if they can live in the soil up to 5 years without having a soybean plant growing,  why would there be concern with just 1 year of drought? 

Like I said, I have never seen an issue before with our years of droughty conditions.  I DO see issues when planting soybeans into fields which have NEVER had soybeans before - even when the soybeans are inoculated.  

Having said all that, I still ALWAYS recommend a farmer to inoculate soybeans - whether pre-inoculated or inoculating on-site at planting time - or both, depending on the situation.   (Doing both when planting into "virgin" fields.)