Thanks for reaching out! Atlaskit is most definitely not deprecated - we have a number of internal development teams working on everything from the core component sets, to media and editor. Recently we’ve re-worked our issue tracking experience - however for now it’s been moved back into an internal system while we find a better way to allow external contribution.
Regarding the outdated styled-components dependency, we’re looking into it. The last few months our core team has been focused on converting the project to Typescript, but that work is beginning to wrap up and we’ll be looking into where to go with our CSS-in-JS solution. Currently a few components such as Checkbox and Button have been converted to use a newer version of Emotion, instead of Styled Components 3.