There are many opinions on how (if) diablo 3 will look and play. It is not even posted as being developed on the blizzard website. One thing that you can garuntee, which is why I like gaming forums, is that these threads (well... in their prime, atleast) and other popular blizzard gaming based forums are read by blizzard employees.
With that being said, you are providing your input and ideas for free. You are giving your 2 cents in the multimillion dollar idea. The stickied threads at the head of this section ARE what we will get, as by popularity.
As for graphics, which seems to be the biggest arguement- alot of people do not wish to play diablo in a WoW like realm; Has anyone taken a peek at
StarCraft II ? Notice how much like classic starcraft it is? Looks very modern and updated, but if it didn't say "starcraft" all over it you could still say: "Woah, a new version of starcraft?"
Also, as it has been previously posted, blizzard asked for(?) diablo3. com
Diablo 3 News Community - for some reason that looks very similar to the starcraft2 website name. It makes one wonder, does it not? (Not sure if they made a monetary offer or not, I just know that alledgedly there was no financial exchange for the domain name)
To go even further into details of marketing on why diablo3 has not been formerly announced as under development (if it is in deed being):
WoW was just released, diablo 2 is dieing (maybe dead, even?). People are purchasing millions of dollars of gameplay every month from quitting the dieing breed of games to play this new fab fav. Being a diablo fanatic, if I was waiting for diablo3 and thought, "Hey, if it'll be out in two years- I can wait it out and keep playing diablo2" they would receive no profit from me for two years. On the other hand, if I was led to believe that diablo 3 would not ever be made, "Eh.. I guess WoW is the next best thing... I'll pay to play monthly and purchase the game."
In conclusion, step back and take a peek through the looking glass. Oh yeah, with the quotes: I do, infact ,call World of warcraft "wow" in RL. (In a bit of a bored and sarcastic tone none the less.. and to you fanatics: Yes, I have purchased and played it.. reminded me that I miss when classic d2 was in its prime.)