It's doable, I believe. Again FF's mess bringing down her general power. I'm sure no one thought she'd pull 505k, 1.7m and 4m worldwide after shaving head, going to mental hospital, losing custody of her children and being overall viewed as the smut of America at the time. No one expected the huge success of that tour, or the way "3" performed.. and of course most recently all you suckahs underestimated "S&S" like she was not featured!
Britney is basically immune to ultimate demise like Beyonce or whatever. Guaranteed, a hot first single that the public loves (really, sadly nobody likes HIAM except us stans).. an epic video and of course her name back out there in a positive light (not her looking old/sick, body double drama, all the stuff that was hitting us pre-FF), that's thousands of consumers back in her hands. During the Holidays, where people are wanting to spend. There will be tons of hype with Vegas shows coming as well, so her opening can be great again. It will be.
I haven't a doubt the era will come in strong and prove to haters they've been doubting since 1999, and prove to those of us who don't think she can do something.
I mean, I'd love to be proven wrong, but I'd aim for around 1.1M-1.2M at most in the US. Overseas, I think she can match Circus, though. 
i love her hair 
