[Baeocystin]

They will mine wherever they can make the greatest profit.

That doesn't mean we will ever run out, or even ever run out of good-quality limestone. It just means that for a variety of reasons (mostly lax taxation laws and a population in poverty that will work for terrible wages) Vietnam is a hotspot for mining in SE Asia, but its total production is a rounding error compared to what is produced in China alone.

There is a lot to be discussed about exploiting poorer areas for resource extraction. It's a subject that goes beyond any one particular resource. But (in the case of lime) it also does not imply scarcity. Keep in mind that lime can be regenerated- the lime cycle is an endless loop.