for the changelog, refer to the wiki - it can be edited by all of you, so if you are aware of anything missing, feel free to edit it - equally, if you are seeing any typos/grammar mistakes etc - obviously, adding screenshots would also be appreciated.
And please don't worry about making mistakes - it's a wiki article for a reason, it works exactly like the community-maintained newsletter: you can all make it better, and ultimately it will be peer-reviewed by core developers and wiki admins, so that the announcement can be locked.
Regarding the wordpress website, note that Thorsten is the one who's apparently doing most of this work, and then keep in mind that Thorsten is also the main guy handling all the rendering stuff (ALS, weather etc), while also doing quite a bit of interfacing between the forum and the devel list community, so he's obviously pretty busy.
If you'd like to help with any of this, you can obviously get involved via the wiki - for the website, my suggestion would be to start a new forum topic and post contents/images etc there so that Thorsten, or Curt, can reuse your suggestions.
Finally, note that this is really where the power of having a community comes from, i.e. different people can create stubs and make suggestions that go through several iterations of being improved before they'll be finished, no matter if that means creating a newsletter, a changelog, a release announcement- or even a whole FlightGear release: it's a process that you get to shape by getting involved in various ways - and the wiki makes that extremely straightforward - while allowing other contributors to focus on other areas, e.g. moderating the forum, the wiki, or core development/packaging a release.
You only need to look at people like Red Leader on the wiki to see just how much of a workload they're taking away from core developers and other contributors by being involved there, without ever having to be told what to do.
To some of you it may admittedly seem like there's some kind of "master plan" in place, but Red Leader is really working "on autopilot" - and whatever is handled by these people, does not need to be handled by other contributors.