It's taken China a long time (in earnest in 1984 and still happening today; political reforms are still very minimial). It's taken South Korea less time (their latest Constitution was adopted in 1988 and their political reforms were farther reaching).
Don't misunderstand - it's going to be a slow process. But I think the latest news is promising. When leaders decide to change policies, liberalization can happen very quickly.
Cheers,
Scott.