If you don't have a lens in this focal length range, and the price of the f/2.8 is a roadblock, this lens is a good idea.
Being smaller and lighter than the f/2.8 it may be easier to hold steady and get better performance from the VR. If VRIII has some new tricks then maybe 4 stops is possible. (I tend to go with the thought that Nikon seems to overstate VR effectiveness by 1 stop.)
Yes, you don't get the same DOF at f/4 as you do at f/2.8, VR or no VR. Usefulness depends on whether you want the larger aperture to get enough light to capture a sharp image or if you are going for DOF. If this lens at f/4 with VRIII is truly effective, then you can theoretically shoot the same scene as with the f/2.8 with VRII, but the DOF will be different.
I've already got the f/2.8 vII so have no interest in the f/4 lens. I have other lenses that are on my priority list. However, if I did not have a 70-200, this seems like it would be worth considering.
Of course, all of this is BS until people get their hands on the thing and and report how well it works. Good god, it may have "flecks" inside the barrel!