The problem is the world isn't shrinking. It's just the wealthy educated bits of it that are. So we're going to have a shrinking number of first world citizens surrounded by ever increasing numbers of the global poor.
Now, if you wipe out poverty entirely and bring everyone up to the same standard of living and education you'll probably see a shrinking global population. But that isn't happening yet and won't happen for a long time.
Actually, it is happening. The western world's wealth has been decreasing over the past 10 years while the rest of the world has been rising out of poverty (for the most part).
Now, if you wipe out poverty entirely and bring everyone up to the same standard of living and education you'll probably see a shrinking global population. But that isn't happening yet and won't happen for a long time.