GCC 15.1 should be released in the next few weeks once all the main bugs have been squashed. Nonetheless, the changes that have taken place for GNAT are already available in the Changelog page for GCC. There are quite a few nice things that I am personally very excited about!
GCC 15.1 has been released, this marks the stable release of the GCC 15 series and the changes listed can now be used in a stable release!
The people using rolling release distros should be getting this new version soon. The people using Fedora 42 have had access to GCC 15 for a bit already