donaldejose your assumptions on close to everything you have posted flat out ignore reality, history and all of the valid arguments everyone has brought up.
1. 4.1mp images from a D2h graced magazine covers, newspapers, advertising and the like. DX has been good enough for 10 years. Is FX better? Yes. Will everything improve and reach a "crossover"? Yes. Does this have anything to do with your suggestion of lenses? No.
What it does show is that the quality attained for publications was attained many years ago. This was the most viable time for your lens suggestions and only the 17-55mm was made along with many variable zooms and macros which many like the DX format for. If any decision was to be made for this range that was was the time when 100% of high end shooters were on DX. The time has passed, and the decision was FX lenses sufficiently covered the ranges or was not economically viable.
Ignoring what market viability means for products and countinue to argue "your desire" is enough to meet a viability is ignoring reality.
Here are the production runs of the FX/DX equiv:
24-70/2.8 G IF-ED = 394,011 Aug 07 - now 87.6k/yr
17-55/2.8 G IF-ED = 184,851 July 03 - now = 21.7k/yr
28-70/2.8 D IF-ED (during DX) 130,740 Feb 99 - Jul 07 = 15.6k/yr
*24-85/2.8-4 D IF (The "cheaper pro lens") = 167,755 Aug 00 - now = 14.6k/yr
24-120/3.5-5.6 G IF-ED VR = 190,940 Mar 03 - Jul 10 = 26.2k/yr
Two things pop out.
1) The 17-55 + 28-70 = 315,591 units made/sold is still short of the 394,011 made in less than 5 years of the new FX 24-70mm. Trend? The FX lens is in overwhelming demand and has sold more than twice as much in 4 1/2 years than the 8 1/2 years of the 17-55mm.
2) The 24-85/2.8-4 "cheaper pro lens" that people wanted, in a 12 year run sold less then the variable zoom in it's 6 year run.
If you were running a company, would you make lenses for the body format that sold the most in half the time, or make something for a body format that sells four times lower and costs almost the same to make? That is what Nikon is forced with and what we are all trying explain.
I don't believe anyone here is trying to be mean. There are many who are frustrated by the continual threads that complain about prices, lack of cheap pro glass, and/or not the range "I" want, which ignores any sort of real viability or the fact that DX has been out for over 10 years and as if this current complaint is "ground breaking".
Thread title: Line of pro 2.8 zooms for DX?
If the Nikon D400 is a "true pro" DX camera, not only in size and function but with Image Quality and High ISO clean images sufficient for magazine publication, weddings and other client work, should Nikon produce a series of professional 2.8 zoom lenses for DX format?
This has been the case for over 10 years and now the largest spenders of camera gear who are more than willing to pay over $1,000 for lenses and gear year after year, have moved to FX. The cheaper pro lens (assuming this is probably the same market of shooters) sold just over 14,000 per year.
Reality of the DX line - The 55-200vr sells over 486,000 units per year, the $1,800 24-70/2.8 lens, sells 87,000 per year and the only pro dx lens made, sold 21,000 lenses per year. That is called not viable.
55-200/4.5-5.6 G IF-ED VR = 2,335,933 Mar 07 - now - 486.7k/yr
70-300/4.5-5.6 G IF-ED VR = 792,426 Aug 06 - now - 144.1k/yr
70-200/2.8 G IF-ED VR I = 270,705 lenses sold from Feb 03 - Jul 09 - 42.9k/yr