GTK+ 4.0 Likely Being Released In Spring Of 2019

In Summary :

While the GTK+ 4.0 tool-kit was previously talked about for release by the end of 2018, that's now looking more like spring of 2019 when this next major version will be released.

Happening the past week was the GUADEC 2018 GNOME developer conference and now the GTK+ team has put out their notes from the planning and discussions that happened pertaining to the next major version of the tool-kit.

In case you missed the recent GTK news, a GTK+ 3.24 minor feature update release is being planned for this fall alongside GNOME 3.30. GTK+ 3.24 will serve as an interim release until GTK+ 4.0 is available and adopted.

When it comes to GTK4, among the items they are still working on are finishing up the drag-n-drop (DND) support, introducing GtkTopLevel and properly handling pop-overs, adding transformations, creating a shortcuts event controller, porting the GtkTextView to render nodes, ensuring the Cairo back-end is performing at least on-par of GTK3, porting various libraries to the new interfaces, and other miscellaneous work. [...]

kindly refer the following link as follow up :
https://www.phoronix.com/scan.php?page=news_item&px=GTK-4.0-Spring-2019-Plans