The last time there was a delay between the release showing up in downloads and the actual announcement, it was because they were waiting for the Pi Zero announcement before spilling the beans about the software. So maybe it is the same situation this time... or maybe not.
The Release Notes are available, and don't indicate that there are very large changes in this release, just some nice incremental updates, bug fixes, and general cleanup. There may be some interesting internal changes; we'll have to wait for the official announcement to hear about that.
These images are compatible with all Raspberry Pi models (0, 1, and 2). I have installed the new Raspbian release from scratch on my Pi2 with no problem, and I have upgraded an existing installation (apt-get update; apt-get dist-upgrade), again with no problem. I have not tried the NOOBS release yet.
It appears that one of the biggest changes, at least to NOOBS, is that Windows 10 IoT has been added. That might be good news for some; it is a no-op for me.
I happened to notice these releases because I was working on the Manjaro-ARM release. Now there's something to get excited about... I should be posting a first report in the next day or so.