Two reasons why regions might change over time

If you mean geographically/biologically - the world is changing, and so will the environment, and with the problems we have now a days, it's likely to change fast in aspects such as temperature (will get hotter), fauna and flora (will decrease), etc.

If you mean politically - some countries might gain more territory trough battles or wars, and some other countries might possible "reclaim" long-lost lands that belong to them historycally.

Hope it helped,

BioTeacher101