It seems Mozilla is planning to change Firefox UI in upcoming versions most probably Firefox 8.0. "Stephen Horlander" has shared some interesting UI mockups of Mozilla Firefox named "Australis" at Mozilla People website.
The mockups have been created for Mac OS X and Windows 7. Some interesting mockups are as following:
Mac OS X:

Windows 7:

Windows 7 Maximized:

You can take a look at other mockups at following link:
What do you think about these new mockups? Like it? Do you also think these mockups look similar to Google Chrome?
PS: If you want to enjoy this mockup UI, check following article:
Download Mozilla Firefox “Australis” Mockup Theme
This article was posted by VG in following section: Mozilla Firefox.
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Alan
Its bordering on ridiculas that Firefox must release a new version every 6 weeks. Every time I get FF just as I want it there is an update and yes I know I dont have to upgrade. The addon makers must be really pi**ed with Mozilla - how do you keep up with them?
Someone
Looks like Google Chrome.
JrColas22
My first thought: Looks too much like Google Chrome.
And I agree with Alan. Firefox was fine with the way it used to be released. Now Mozilla has just released version 4.0, and with only one update (4.0.1), Firefox 5 came out. I'm typing this right now and I just remembered I was using FF5, not 4.
I was excited about FF4. FF5 came out, I didn't realize it. Now I realize that Mozilla is somewhat copying Google Chrome: No more "http://" and now this UI.
Tangmeister
I myself don't care if they copy Chrome, since that's progress! :D trollface.jpg
But I do feel annoyed at the rapidly advancing updates and the pains for users to update themselves- Chrome is automatic and seamless there.
Interesting, but inconsistent with the general Firefox "feel". :'( imo
I
Address bar and tabs on the same row as well as a big back button. Damn you M$, copying from Mozilla!
Am I... am I doing this right?
Mushaf
Totally awful!
I hope somebody will make a FF4 theme for FF8 if Mozilla really changes the interface like that. It's like blindly copying Chrome and IE without thinking of the usability.
Rtyh-12
Looks cool! I don't care if it looks like Chrome, Chrome looks great.
Swapnil
Cool mock-up by Mozilla. Mozilla is now on Google's train and the station is Firefox vs. Chrome.
Amiel
IE9 still looks the better in my opinion :)
Jack
Do people really care about stuff like this?