"Limbo was never a defined truth of faith. Personally -and here I am speaking more as a theologian and not as Prefect of the Congregation- I would abandon it since it was only a theological hypothesis. It formed part of a secondary thesis in support of a truth which is absolutely of first significance for faith, namely, the importance of baptism. To put it in the words of Jesus to Nicodemus: 'Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter the Kingdom of God' (Jn 3:5). One should not hesitate to give up the idea of 'limbo' if need be (and it is worth noting that the very theologians who proposed 'limbo' also said that parents could spare the child limbo by desiring its baptism and through prayer); but the concern behind it myst not be surrendered. Baptism has never been a side issue for faith; it is not now, nor will it ever be."
-Joseph Cardinal Ratzinger in Feast of Faith