God doesn't know jack. That is why he made us the way we are.
On Limbo, this was a painting in a man's mind. Nothing more. It doesn't exist.
All humans go directly to heaven except the ones that understand the 10 commandments and go against them.
Seems to me God was disappointed several times throughout Biblical history. Even regretted decisions He had made from time to time. Hard to be disappointed if you always knew the outcome in advance.
My hypothesis is that, when God delegates decision-making via free will, He doesn't cheat and peek at the answers.
I understand that. The theological problem with the fate of those who die before reaching the age of reason is that they cannot make a decision for which they can be held morally responsible. God's "foreknowledge" would not change that.