They should launch 6 classes.
Definitely Amazon. With a modern wind force and unleashing lighting fury what not.
The other class is more tricky as necromancer was the latest released and pally or crusader would be a third melee in the lineup, making it seem overcrowded.
Amazon > Necromancer > Pally
I would definately like to see a trapper again.
Preferably in a form of a pirate or scroundel.
Also this might upset many, but they should have invented gun powder already, so My ideal class would be a pirate with options to go melee(dagger, short swords), ranged (rifles and bows) with traps.
Second class should be a paladin/necromancer variant good example for something I would really enjoy was Chosen from Warhammer Online, a heavy shield wieldin tank specialized on debuffing enemies, give him some summonable friends and you get the best from both paladin and necromancer pets, dark and tanky.
I feel like there are too many tropes they need to fulfill with only 2 classes. They need a summoner and a range/bow character.
Would like them to be Amazon and Necromancer (D2 version).
But then you are missing the holy warrior trope. I wonder which they are going to abandon. I hope itās the holy warrior they abandon and we get necro/Amazon. Then expansion would be assassin(or other character who does traps) and crusader/monk/or paladin
Diablo 4 Classes so far:
Barbarian - Diablo: Hellfire(unfinished hidden character) and Diablo 2
Sorceress - Diablo 2
Druid - Diablo 2: Lord of Destruction
The other 2 will probably be from Diablo 3. Iām going to guess the Crusader, and Demon Hunter. Or, they might keep it D1/D2, so possibly Paladin, and Rogue! 
Spear Amazon - at least for expansion, better as one of the last 2 classes.
no pally please.
Also why cant the barb wear shield and sword. I love fighting with shield. Would be nice to see some special attacks just with the shield for example.
Thank goodness some of you arenāt devs.
Obviously we will get a ranged class as itās missing, and I want one. Hopefully not with rockets and other not diablo BS.
The second class is tougher. No proper pet class yet, and there needs to be. I want a necro for sure.
But the paladin would also be great.
Has there been any mention of auraās coming back?
Something new and oldā¦ I would like being Blizzard a DEATH KNIGHT type character.
Apply similar abilities from WoWā¦ boom game changer!
And old ones likeā¦
Amazon/Demon Hunter- Range type
Assassin/Monk - Melee
Paladin/Crusaderā¦DEATH KNIGHT!!!- Aura
Nercomaner/DEATH KNIGHT!!! - pets
Death Knight hands down!!
for the two slots probably left Iād say one will be an archer type class.
I am totally open for the last slot.
I would like to see Necromancer to be added. I donāt care for the rest.
i think there is like 99% chance that one of the two remaining classes is ranged with bow. There is a crossbow in one of the photos shown during blizzcon.
And for the 5th class i would like to see paladin or something completely new that didnt exist in diablo so far
Paladin is so much better than the crusader. Paladins could be built so many different ways and still had so many fulfilling builds. I would like to see paladin and amazon. Didnt care for DH either being able to through javelins and light up an entire mob or use bows and shoot them all down being able to swap between melee and ranged, thats what we need a class that can swap at any moment between ranged and melee. I really loved the assassin so i would take the assassin as well.
Iād like to see all the d2/d3 classes really and a couple new ones (maybe a death knight type). I hope development goes that long. But Iād like to see Paladin in the first round. I think with all this darkness/evil, it needs to be purged with the light and have some justice administered.
My favorite d2 paladin was the Smiter. I had high hopes for it returning with Crusader, but they missed the mark with Shield Bash. So I hope a strong holy shield build can be done right in D4
Something like Cleric or Shaman basically something we havenāt seen yet.
Shaman = WD, Cleric = ā¦useless? -)
Same as you. I always go for the archer and i cant see them not having a ranged class.
I see them putting in something like Amazon ranger or possibly valkyrie
I swear some of you do this to troll. We do not need hippy necromancers
At some point (probably in an expansion not on release) id like to see a plague doctor/alchemist themed class. I just think it could be a cool class aesthetically. Not really sure what it would play like tho. Havnt thought that far ahead.
I honestly think that they need the paladin/crusader. We have to see a holy warrior in diablo.
The 2nd class should be an Amazon. We need a pure range class and she is a D2 favorite of many.
I believe the druid could be the filler for the summoning class everyone is wanting to have between spirits,ravens, and maybe even some ents. The druid could also fill the roll of a secondary melee/tank class with bear form. Possibly eliminating the need for the paladin/crusader and could come out with more of a dps oriented holy class.
With the new skill system and points i feel like turning a hybrid class such as the druid and making it feel more specialized is definently a possibility.
Lets see. I didnt read through everything but maybe for a new class. Or a mix. Maybe a blood knight. Sortof like a paladin, just maybe not holy. Gives off a bunch of debuffs to enemies and maybe like health buff auras to friends. Than he can be dark and gorey. Use offensive blood magic and still use a shield and sword? Just throwing an idea.