Cargo rates will just go up and that's it. It could be that some stuff which is currently flown will have to switch to surface transport, but generally speaking 100% rise of fuel price will get cargo rates to rise by 30-40%.
Fuel represents anything between 25 to 40 % of total cost at cargo carriers operating modern equipment (744, MD11 and newer), CV just above 35%, LH less than 30%.
So instead of paying $4 per kilo, shippers will have to pay $5.5. Typical stuff flown longhaul costs over $100 per kilo, if the fuel cost would double, overall commodity price at destination will increase by 0.5-2.0%. Hardly end of the world.
Fuel is not a problem for the industry. The problem is some industry players who dumping the rates in order to get their market share or to get a quick cash. On a macro level, for sure, supply and demand level are important, but this is outside airlines control.