The developers of the GTK library plan to form an experimental 4.90 branch at the end of the year, which will develop functionality for a future release of GTK5. Prior to work on GTK5, in addition to the spring release of GTK 4.10, it is planned to publish a release of GTK 4.12 in the autumn, which will include developments related to color management. The GTK5 branch will include changes that break compatibility at the API level, for example, related to the deprecation of some widgets, such as the old file selection dialog. Also discussed is the possibility of stopping support for the X5 protocol in the GTK11 branch and leaving the possibility of working only using the Wayland protocol.
Of the additional plans, one can note the intention to use a more expressive programming language than C for the development of GTK and a more functional compiler than is provided for C. What programming language can be used is not specified. This is not about completely rewriting all GTK components in a new language, but about the desire to experiment with replacing small parts of GTK with implementations in another language. It is expected that the possibility of development in additional languages will attract new participants to work on GTK.
Source: opennet.ru