There has been an official and alternative version of the default theme for many operating systems for a long time. What I mean is that both Windows and macOS, Android or iOS (13, as of this month), among others, usually have a theme and another version of it by default, usually in dark. Yaru is a very popular theme in Ubuntu and they are already working on a dark version that, if nothing happens, will reach Eoan Ermine, but now we know (via Linux uprising) that there will also be a clear version or Light.
The first thing we have to say to calm the emotion of those who want to use this theme in Ubuntu is that it is not known if it will reach the Eoan Ermine which will be released on October 17. What is certain is that it is a request that has been accepted, which means that there will be a Light version, but it is not known exactly when. In the future, which may coincide with the release of Ubuntu 20.04, there will also be a hybrid light-dark theme.
There will be dark, light and hybrid themes from Yaru
Its developers already advanced there would be a clear theme, but they seem to have been having trouble with the colors. That is one of the reasons why the hybrid version will exist, that at first there were problems with the buttons of the upper bars when compared to the background. And so the idea of creating a completely clear topic like the one you see in the screenshots of this post.
The three versions of Yaru (light, dark and the union of both) are in development, the dark version being more advanced. If I had to bet, I would bet everything that the "Dark" will reach Eoan Ermine, but I would not bet that it will arrive with the other two options. There is still more than a month to go until the official release of Ubuntu 19.10, but they will probably take things easy and prepare everything well for the release of the next LTS version, the Ubuntu 20.04 which will arrive in April 2020.