GWT has been open sourced. I am hopeful that this can only be a good thing. There is still at least as much activity on the project as when it was not open source. The 2.6.0 RC1 release notes look great. Just recently a Google employee was working on a bug I was tracking. And there's the GWT Create conference coming up.
I was worried about GWT when I saw Dart coming up and getting attention, because I've enjoyed writing apps in GWT, and would like it to continue to be an option when we're scoping new projects. So far what I'm seeing from the new status of the project is helping to keep my confidence.