This process has limits. Older chinese aren't short because they're old, they're short because of nutritional stress.
Also, shrinking isn't a linear process. You spend most of your life only shrinking a small amount; most of it happens toward the very end:
> For both sexes, height loss began at about age 30 years and accelerated with increasing age. Cumulative height loss from age 30 to 70 years averaged about 3 cm for men and 5 cm for women; by age 80 years, it increased to 5 cm for men and 8 cm for women.
Also, shrinking isn't a linear process. You spend most of your life only shrinking a small amount; most of it happens toward the very end:
> For both sexes, height loss began at about age 30 years and accelerated with increasing age. Cumulative height loss from age 30 to 70 years averaged about 3 cm for men and 5 cm for women; by age 80 years, it increased to 5 cm for men and 8 cm for women.
http://www.ncbi.nlm.nih.gov/pubmed/10547143