In the next major release of MATE it is going to support GTK3 while still being compatible with GTK2 as well. The development is mainly done by Semmu under Google Summer of Code 2013, with the help of the main MATE developers. You can follow the development at Semmu's GSoC blog.
This site is updated frequently.
|libmatekeyring||Dropped - replaced by libsecret|
|mate-keyring||Dropped - replaced by gnome-keyring|
|libmatewnck||Done - may be replaced by libwnck|
|libmateweather||Done - may be replaced by libgweather|