Mozilla is changing plans
The Mozilla Foundation stops with developing new features for the seamonkey project. But Mozilla is still planning to give security patches and bugfixes. Mozilla is planning to get it’s focus on FireFox and Thunderbird. The 1.8 version of Mozilla Suite will probably not leave the beta stadium.
As mozilla says:The ongoing alpha and beta releases of Seamonkey 1.8 have suggested that the Mozilla Foundation itself will be creating a 1.8 final release. This is not our plan. The 1.8 releases have been for testing our backend. We intend that the 1.7.x line of releases will be the last long-lived, maintained versions released by the Mozilla Foundation. There is no doubt that the series of 1.8 alpha and beta releases have caused some confusion about whether there would be a 1.8 product released by the Mozilla Foundation. In addition, a set of people have done a non-trivial amount of work on 1.8 features, thinking this would be part of an official Mozilla Foundation release. This has been a major error on our part. These contributors have reason to be unhappy with us. We can only apologize, at the same time recognizing that apologies only go so far and can't fix the error.