OK, so looking around, the 70-200 competition appears to be (all prices B&H for sanity's sake...)
Nikon f/2.8 $2400
Sigma f/2.8 $1400 currently rebated lower
Tamron f/2.8 $770 No VR, not really sure how apt a comparison that is, although both the Tamron and Sigma have largely positive ratings with over 100 reviews each.
If the f/4 comes in around $1500, there's probably some niche for it. If t comes in closer to $2K, well, I don't get it at all.
Tamron has a VR version announced but not released - If I'm not mistaken the price was expected to be around $1,700 (equal to sigma) but I'm sure it will settle around $1,500.
Tokina also will be coming out.
As Rx4Photo and others have said, the 24-120vr & 16-35mm f/4 is $1,300 - My guess it will be about the same or a bit more. Thats about 46% less of the 2.8.