Honestly, I will be STUNNED if D4 isn’t announced. Like, totally floored. Not only have we had a ton of credible sources say it’s coming, but even without those, I’d expect Blizz to try to “make right” for last year.
This specific leak seems likely given the source but I’ll remain guarded in case the guy decided to troll for some reason or got bad info from his sources.
The last “real” leak is a twitter picture of what obviously is a D:I picture of a barb.
So there is still a chance that the “big” announcement could be that.
mount and horses < enigma
I sincerely hope there won’t be mounts. As much as open world is fun, Diablo was always about the crypts and stuff, so I hope that’s wrong too. If there is a much larger world, travel might be required, but… waypoints! If this stuff turns out to be true, my -10 expectations just went to -12. Oh the pain… but of course they will. Of course they will add mounts! If they add mounts they can sell mounts. They’re gonna crowbar in every conceivable type of cosmetic item they can think of to milk more money out of the players. I just made myself sad. 
Why can’t there be mounts that take you to crypts and dungeons? Riding off into the distance and seeing that Massive tower recently taken over by demonic hordes…that could be very impressive and set a precedent!
D3 is already an open world outside of mass player hubs, with waypoints. So not hard at all to imagine this happening.
Either way, hope for the worst and I am sure you will find a way to be frustrated regardless!
FWIW, there is nothing wrong with cosmetic MTX, some people really like that stuff and WANT to spend their money on it…imagine that!!! People buy what they want and talk about what they want!
Because it’s dumb. Yeah. I already have a gripe with how fast D3 is. I hate speedruns, always have. Where’s the challenge, where’s the adventure, where’s the fun? All this zipping around from elite pack to elite pack… Diablo was never a racing game. Adding mounts seems completely unnecessary to me. However, if being mounted vs not being mounted somehow slows unmounted gameplay down a bit, I’ll give a chance.
Oh there’s so much wrong with it, and also with people who like it and waste hard earned money on it that I don’t quite know where to start, but that’s just me. We all have our opinions. Cheers! 
How do you see the tower in the distance in an isometric game?
I have read it that mounts will slow things down and add a layer of exploration, not speed things up! I think that this means the battles in dungeons and crypts will be more like that D2 pace, and feel like an RPG rather than an Arcade game. Not sure there is going to be mounted combat, that seems to be pure speculation atm.
The thing is, if I want to spend my money on an appearance in a game, I WANT TO SPEND IT THAT WAY, so it is not a waste. Sounds like to you it is, and that is also fine as you said, we all have our opinions, and I like trying to give a larger group of people what they want.
See Lost Ark for details
Or those things could be included in a $60 purchase. Rather than parted out for the whales. But cAAApitalism always wins.
That wouldn’t be entirely horrible! 
Mostly this. And also I think it should be earned in-game by playing the game, not paying for it with real money.
Well, I’m sold. 
Personally I like mounts but and it’s a big but - The size of the game has to support them. A game on D2 or D3 size does not support riding very well, or mounted combat.
Secretly I think I want a Diablo RPG more than a D4, but that’s my bad I guess.
No. I’m not going to play an entire game just to figure out what you’re talking about.
Mounts, huh? I’m not sure how to feel about that to be honest.
On the one hand, I like the idea of exploring Sanctuary, of being able to stumble across a randomly generated village with NPCs and what not, or some cave filled with monsters, or some runestones with a puzzle to solve. I like the idea of exploring and discovering and world building a whole lot.
On the other hand… as others have said, if there is a large enough scope to the world that mounts are even a potential to be added, then the spreading of mob packs in the open world will no doubt feel bad.
One thing the D3 devs had going for them was a direction of not breaking down the action. Its something I recall them mentioning ages ago when D3 was in development. If I’m riding from one pack of mobs to the next, well… that’s a break in the action.
LMFAO, MTX are the most successful in China, where it is Communism, just saying…
On one level I get this, but on another level, if we want good games, developers need a revenue stream otherwise there is no incentive to continue making content.
Is it out of the realm of possibility that D4 could be a 3D isometric game with adjustable views when riding mounts, etc…?
Not sure how this would work or look tbh.
In one way, I get that… because support and more content can be a good thing. The other side of the coin is that they’ll just keep messing with it until they eventually make the game unrecognizable to the original product (as they tend to do). It’s a double edged sword, and it’s hard to know where’s it’s gonna land. 
EDIT: I think the reason D2 is so good is that Blizzard finished it and left it while it was still good.
Except that’s just not true at all.
Expansions generate money, provide content, and can make good games. You don’t need a constant drip feed of skins to make good games.
The only reason the drip feed exists is for revenue. Not for good content or support.
Fair point, WoW suffers from this pretty bad. Had a friend who played in vanilla, quit in BC because belves went Horde, and then got convinced to try it recently. He was shocked when he saw people riding by him on Elephants, Spiders, Water Bugs, etc… Said it didn’t feel remotely like WoW.