We will soon be releasing the first beta for the next generation of the ArcGIS API for JavaScript - 4.0 beta 1.
Until then, you can find some information in the UC Q&A | What is new and exciting about version 4.0 of the ArcGIS API for JavaScript?
For feedback and questions about the 4.0 betas, please post in the ArcGIS API for JavaScript forum and make sure to tag with 4.0beta.
Interesting ...
Will there be a Table of Contents widget in the JSAPI 4.0? Hoping. We don't need it for all apps, but for some, it's just helpful.
Chris...thank you for this good feature suggestion.
Bjorn Svensson if they use WAB's TOC code, can you pass along that they need to make it more hierarchical? If you close a group it does not uncheck the sublayers. Basically, it should use the behavior and GUI of Nianwei's AGS TOC. or the hierarchical menu system in any application does, whether it is ArcMap or WIndows Explorer. Closing a group should uncheck and close sublayers. Perhaps this was just a bug in the new WAB T.O.C. And so should patched in WAB too. Should I include screenshots or is that enough detail? And thank you! Looking forward to 4.0! Vectoring tiling, 3D etc sound awesome!
For feedback about WebAppBuilder, it's better to post in the WebAppBuilder forum:
Web AppBuilder for ArcGIS