The title and the description ask two different questions.

I do not think people are optimistic about the future. Back in the late 90's/early 2000s yes, people were very optimistic. Everyone was so thrilled to get to the 21st century. Now, people seem clinically depressed, technology is no longer something designed to make you happy, or make your life easier. It is just a battle to control your attention and sell you garbage.

Will people be happier in the future? Honestly I don't know. Anyone can "decide" to be happy to some degree. As a large group/society, no I don't think people will be happy.