Currently numerous bugs are still unresolved in Fedora 18. These bugs have been marked as important and their resolution is necessary before Fedora 18 is released. The developers also need to solve the problem of incomplete test matrices, which are still not ready.
Another go/no go meeting will be held on 30th of August and if the developers give a green signal, we can expect Fedora 18 alpha to be available on 4th of September.
Fedora 18 focuses on bleeding edge software, and it's quite difficult to create a stable operating system with less tested software that is suitable for masses. While developers put quality first, it's normal to see the release dates pushed further.
Edited by: Zachary Bittner