There has been a decided shift toward optimism in regards to the salvation outside the Church in recent years, but I think this actually runs counter to the developments of twentieth-century Catholic theology--at least, the thread that has been most completely absorbed into Church teaching through Vatican II, John Paul II and Benedict XVI.
That development has been in the direction of more explicit Christocentrism and toward approaches which remove the arbitrariness in the associations between Christ, his Church, the sacraments, Christian morality, and salvation.
Thus, salvation is not just an arbitrary reward for a good life, carried out with the help of the Church and the sacraments. But (in a sense) salvation is life in Christ--it is life as member of Christ's Body, which is his Church, which is constituted by the sacraments.
This actually makes salvation of the unbaptized (or even non-Catholic Christians) harder to explain than explanations that focus primarily on forgiveness of sins. It is easy to imagine forgiveness of sins occurring outside the normal sacramental economy--even within the sacramental economy, there are various ways that sin is forgiven. But when salvation is seen as being not ultimately distinct from the Christian life--that is, following Christ, living a sacramental life in the Church--then salvation for people who are evidently not living that life is much harder to explain. What would such a salvation even mean?
I guess you fall back on the fact that basically anything good that anyone does is ultimately due to grace. So, whatever is good in anyone's life must be attributed to grace at some level . Thus, grace is available in some form to all, and all have the ability to accept or reject that grace. And, to the extent they accept that grace they actually are living in Christ. Still, you can't take that very far without again reducing the requirements placed on Christians to arbitrariness. If salvation is life in Christ and we have a decent idea what life in Christ looks like, then--while we can certainly withhold judgment on any individual, since judgment belongs to God alone--at least on the face of it, things don't look good for most of humanity--which would be in accord with what Jesus said about the narrow gate.
That doesn't mean we can't hope that the truth is otherwise, but that hope seems to have slid into optimism, which is certainly not warranted--either by scripture or the majority of the tradition and common sense of the Church through the centuries. While the Church heavily qualifies "extra ecclesiam nulla salus" these days, I suspect that, for the most part, when our ancestors said that, they more or less meant it--even if they might admit some exceptions.
I expect that the sense in the Church will eventually shift back toward the historical consensus--though perhaps not quite to the pessimism of some eras. It's possible that the current attitude is an over-correction for a distorted pessimism, and we'll find the reasonable mean, which allows for God's grace to work in unexpected ways, but sees the direness of the evident neglect of the ordinary means which he has publicly revealed.
The current optimism seems to go hand-in-hand with the optimistic cooperation with "men of good will" that comes from John XXIII and Vatican II. It's hard to see this being sustained as the "men of good will" increasingly turn on the Church.
