Will the nvidia 6 series be released all at the same time ?

No people here knows it, except the nvidia guys, because they are going to release it.

In my opinion it's going to be like AMD, first the flagship ones, then fastest, then the low-end, then the mid-range.
 
It might be a repeat of the Geforce 3 series that was only released for the mobile segment. I don't believe the performance numbers and charts of how Kepler was supposed to be faster than any thing before.