Original: Failing human intervention, and assuming that a population of about 1000 can survive that long, natural tree hollows will begin to develop in the Black Friday regrowth as the trees reach about 150 years of age in the second half of the 21st century, and numbers begin to climb again.
Simplified: Without help from people, and if population of about 1000 can survive for another 150 years, natural tree hollows will begin to develop in the trees that started growing after Black Friday.