I have been wondering about this for the past week now myself. I entered 2 sessions in Help Request for assistance and I think I figured it out.
[Session 1]
[18:21] Gaybot Foxley: Hi folks. I was wondering if there is going to be any kind of software update tomorrow. A previous blog entry says the First Look viewer is going to be an official version sometime this week.
[18:50] Mia Linden: Hello Gaybot
[18:50] Mia Linden: u need to read the blog
[18:51] Gaybot Foxley: hey
[18:51] Mia Linden: there is an update scheduled for tomorrow
[18:51] Gaybot Foxley: Oh ok
[18:51] Mia Linden: its been posted since Friday i believe
[18:52] Gaybot Foxley: Oh, so its an old post, its just a little confusing. One post says theres going to be a new release and another says no release for the 2 hour downtime on wednesday
[18:53] Gaybot Foxley: So that means tomorrow no update, but this week there will be an update sometime?
[Session 2]
[19:20] Gaybot Foxley: Hi, its me again, lol, i got disconnected. I just have 1 more question. Is a new version of First Look on the horizon?
[19:36] Gaybot Foxley: Okaaaayy, nevermind, i just refreshed the blog and it shows a new First Look viewer. bye bye
The next thing I know there is a new viewer posted on the blog, lol. The confusion I think is because the normal viewer is always released on Wednesdays with approximately 5 hours of down time. The normal viewer is always required to access Second Life. The First Look viewers are released on any day of the week and are optional upgrades. Tomorrow there will be no update and 2 hours of downtime between 7-9 AM SL time. The new First Look viewer is available to download here.
http://secondlife.com/community/firstlook.php