I don’t mean to speak on behalf of the devs here, but they are hard at work on the project and have consistently warned against marketing an unfinished product. The previous videos, in my mind, were only to give awareness to potential backers and to gain publicity for the project. I have no doubt they will provide us a new video in the coming months as they flesh out the gameplay so we can have a legitimate gameplay video. But the video may not live up to expectations as it will obviously still be in Alpha.
Nonetheless, I am certain they will unveil their video as close as possible to the beta launch, so that they may show off all that they have accomplished. This may mean by the end of this year they will send out a high-quality video with gameplay you may one day see when you play it yourself