One basis for speculation is on the unfilled niches of the launch classes known so far. For example, Diablo 4's Barbarian is the upfront melee character, while both the Druid and Sorceress check all the boxes for the magic classes. This means that the remaining classes may be some type of holy class, some type of ranged class, or something somewhat special. Of course, there's a ton of possibilities, but having some form of ranged class in Diablo 4 is a given.

Due to its unique style in Diablo 3 and its overarching Diablo IV Gold popularity, the obvious inclusion for a ranged class in Diablo 4 is the Demon Hunter. However, to say that it's the best or only possible class to fit the slot isn't accurate. Indeed, a variety of other classic Diablo classes or even a new class could fill the slot. There's even some indication because of the Necromancer's DLC role in Diablo 3 that the Amazon will join the Druid in Diablo 4. Essentially, the Necromancer could have been initially replaced with the Amazon or the Druid, so including one in the launch class line up for D4 makes the other slightly more possible. Either way, disregarding that and other classes, this remains a double-edged sword for the Demon Hunter.

Diablo 3's Demon Hunter was Special
As aforementioned, Diablo classes tend to fill certain niches and this intends to include a sort of "Wildcard." These are classes that aren't necessarily restricted to something by necessity, instead being a unique class that eventually stands out for the game. Whether this is intentional or not is up in the air, but it's as obvious in Diablo 2 as it is in D3. In Diablo 2, this was the Necromancer. Even today fans clamor for the Necromancer of the D2 days, and this popularity is at least one reason for why Diablo 3 added Necro as DLC.

The same could be said for Demon Hunter in Diablo 3. It was the stand out Wildcard, and while arguably this could have been the Witch Doctor, it didn't really hit the same strides as a watered-down replacement for the Necromancer. As such, it would make the most sense to see Diablo 3's Demon Hunter to go the same way as Diablo 2's Necromancer, joining the subsequent game post-launch, not at launch. This leaves the "Wildcard" entry for Diablo 4 in the air, and Diablo 4 Gold buy  though the Demon Hunter is less likely as a result, this Wildcard class may just be a good surprise for fans of the franchise.