Could, may or might convey the idea of future possibility. Of these, may expresses a stronger degree of certainty that an event will occur. For example: The temperature is dropping.

What is the future tense of could?

The use of 'could', 'would', or 'will be' all imply future tense. The past tense version would be: "You could not have made me happy, and I am convinced that I am the last woman in the world who could have made you so."

Could is past or future?

When could is used as the past tense of can, it refers to an ability that a person generally had in the past or to something that was generally possible in the past ("When I was younger, I could run for miles," or "It used to be you could buy lunch for a dollar.").