Its a much more delicate balance than you make it seem. Blizzard fans are braced for a failure and ready with their refund requests. IMO this is more prevalent now than any time in history and true for Bliz more than any other company. I agree with the general sentiment about the market in general, but things are greatly exacerbated for Bliz right now. You can tell they are really trying to come back from their recent failures (as evident by hiring an outside company to work on D2R).
They made very clear statements in their reveal; the game is based on the original, its designed for nostalgia, they have a 70/30 design philosophy. They were very clear about what exact changes they have planned from the original. Also they stated a 2021 release, which limits them from making significant changes which will take a lot of time to develop, especially with their “turn it off” philosophy where you can turn the changes off, even the graphics.
Note that in WoW Classic they changed almost nothing and has been a huge success. Bringing back an old game from early 2020, giving it some graphics updates and leaving all the mechanics (including the bad ones) alone = success.
If they release D2R with anything less than what they have promised, it will be a fiasco for them. After refunds and embarrassment, they will lose more money then they gain, especially since fans will lose all faith in them and stop preordering their games.
So there are two scenarios:
A. They release the game with sweeping gameplay changes going against everything they have said. There will be another outcry of Bliz saying one thing and doing another just to make a quick buck. There will be such a massive refund push that it will make headlines. At this point a huge percentage of the population will refund on principle alone. It will be a complete fiasco that further damages their reputation, overshadowing any money this project makes.
B. They release the game exactly as it has been presented, old amazon and all. Most people will stay because D2 has always had solid gameplay and the new graphics are overall mostly cool even if you don’t agree with some of their choices. Sure it will carry forward some 20+ year old blemishes, but its a remaster so there is reason for them to be there. Of course there will be some refunds and complaints that they didn’t listen to the fans, but fans of the original will push back against them without Bliz having to even get involved. The argument people will have is “the game is exactly they way said it would be … but that’s not the game I wanted!”. Well we all want things we can’t have, the problem is about saying you’ll do something and then not doing it.
As for releasing the game with little changes then coming out of nowhere and changing core game play mechanics, well that depends on the market. If releasing the game with little changes blows up in their face, they are sure to try and stem the bleeding by making sweeping changes to fix it. But if the people love the game the way they released it, there are no problems and they are unlikely to change anything.