How would SCOTUS rule on California's Prop 8? With what consequences?

I miss no points.

Here is the actual reasoning:

State wishes to encourage and reward the conception of children
State accomplishes this goal by creating a legal state called ‘marriage,’ limiting it to men and women, and giving tax and legal advantages to couples in that state

No, because the rational basis test would not be used.

Who cares?

For about the sixteenth bazillion time, you cannot attack a law under rational basis by asking, “Well, if that’s the reason, why don’t they do this other thing that is an even better way of advancing their interest?”

Stop doing that. It’s not part of the rational basis test. I have no idea why people continually return to asking that question, despite being told repeatedly that this is not how the test works. It’s in the quoted text right above: we do not care if there happens to be a better or more efficient way of advancing the apparent state interest. Can’t you see it sitting there, waiting to be read and understood?