There is quite a lot of software that really needs an Omega release.
I have seen Gamma used at a couple of work places. The last place used it to indicate the sites that got the GA release first. These sites were referred as our Gamma sites, and were not necessarily our beta sites.
The other usage I have seen is to call software Gamma instead of Release Candidate.
I think that part of it is the death of the version number in web based software (and to a lesser extent in non-web). Look at all the big web based stuff and you almost never see a version number. What version is Gmail at?
I’m sure that the developers still use version numbers internally and still do releases. At least on the bigger projects; very small project can get away with continuous hacking and throwing it over the wall, but a project the size of gmail must have discrete releases with all the appropriate stages.
But they don’t show the version numbers in any prominent places any more. And getting back to the point, once you no longer tell the public about what version you are on and once you no longer make a big deal about releasing a new version, then the whole nomenclature around releases loses its purpose.
Some things like ark survival evolved have a small chance make it to gold stage as the devs are constantly adding new stuff and so the game is caught in an almost endless loop of development somewhere between delta and full release