A more accurate title might be: "world's biggest chocolate-maker tries to prepare customers for higher prices by disingenuously claiming that we will run out of a renewable resource."
I distinctly remember how several years ago Mexico manufactured Tequila shortage by claiming that disastrous weather led to a shortage of agave fruit. At least this was a story given by Canadian liquor stores to questions why Tequila prices were hiked by close to 50% almost overnight. I kid you not. They also issued assurances that once this pesky Mexican weather normalizes the prices will go back to normal. You guessed it - they never did.
Consider that Theobroma cacao only grows well and healthy in the shade, in the middle of the rainforest, it's natural habitat, which is increasingly rare or protected land.
It's also grown by small scale farmers, because it's labour intensive, and they don't know/don't care about managing the forest properly, further increasing deforestation, and endangering the crop itself.
Today's practice is to grown it under sunlight, in poor soil, which requires large doses of herbicides and fertilizers, makes it susceptible to diseases and shortens the lifespan of the tree by 1/2.
On top of that, prices have been increasing for the past 10 years, but I've only seen the production go down here in Brazil. We went from exporter to importer. The invisible hand of the market is not fixing it either.
So you can't assume it's sustainable just because it's not oil.
The article is written in a fantasy world where neither supply nor demand can be altered. Amusingly, while discussing the problem (farmers are switching to more profitable crops) it also discusses the automatic solution (decreased supply will increase prices which will decrease consumption and increase production).