First
Diablo II remaster will beat Diablo IV on sales, because people are disappointment from D3, total fail and management of patches they made it and put the game in worse place!
Second
Diablo IV trailer was AMAZING JOB! but when I saw D4 beta or alpha version idk how to named. I was “here we go again” total disgusting like D3, same mechanic, same core. I just don’t like it, it is so similar to Diablo 3!
What people… What I don’t like in Diablo 3, trade - economic system is dead, AH is… haha… And why they make so many different difficulty(same an idea devs put in WoW ratail… why you put same an idea in different game i can’t understand).
I totally understand you(Blizzard) have casual and hardcore people and you want keep both type of players. Guess what, you gone lose hardcore player with this stupidity. Maybe casual player type is better for wallet… idk
In Diablo 4 gameplay videos:
I don’t like this type of interface I feel it like Console type.
I don’t like hotkeys 123456 left-click right-clock, I mean same version of using ability… same gameplay like Diablo III
I don’t like camera’s angle
I don’t like animation style (but this I can swallowed)
Third
I don’t know what exactly devs wanna make with Talent tree. But if they wanna make it awesome, make it RICH with a lot choices. Unlimited choices for building(In D2 you have over 100 points), you can make and a lot items with different type of ability stats etc. This mean different tactics and way to play.
Someone said will be Open World idk what you mean, but don’t make it 4pp limit game(console style) in D3 that was AMAZING FAIL.
Don’t ever nerf difficulty in Diablo game!
oh I forget, Paragon leveling was worse thing and don’t forget to make duel system out side of city 
ps. If you wanna make something great don’t be lazy!