Those thermos bottles require quite a bit more energy to produce than a package of styrofoam cups. And I bet the # of thermos bottles being disposed would shock you. I see people at work change theirs out regularly. Then there are the ones you pick up at conferences or as cheap prizes with a coating that starts coming off after a few uses because they are produced in bulk in China. 

There are plant based packing and insulation products. None that currently offer all the benefits (low price being most obvious) of styrofoam. And I am sure plant based products used for packaging have their own environmental issues that aren't publicized yet. I know there has been some success with formulating plastics so they biodegrade without sunlight. I think that is probably going to be the best solution long term for the environment other than returning to a hunter-gather culture.