The devs have stated that they don’t want to bring any of the previous classes back in future expansions. If the “sword and board” archetype still needs to be there, what are the options?
Necro can already use a shield offhand
When did they state this? Source?
They mentioned the new class wouldn’t be one seen before, I don’t think they ever stated any future classes they were bringing out wouldn’t be previous ones. I could be wrong on this though.
Sword and board could easily still makes it way, but you can’t think of conventional means of naming them. If the leaks are true and “Spirit Born” is the name of the new class with a glaive as a weapon, then anything goes in terms of naming. They could name a new Shield class just “Protector” or “Guardian” or “One who blocks” for all we know. You can’t think in terms of what’s already out there.
Blizzcon, but I extrapolated for VoH and beyond
My list was just some examples that I could think of, you can create your own class in this thread.
I was thinking something similar to Paladin/Crusader. It’d be similar, but not the same. Like Templar. Maybe the D3 Templar order comes into effect? Lyndon from D3 started his own city, so it’s a possibility. I was also thinking that maybe a sword and board class would be one of the knights penitent.
That guy is currently in Backwater, Hawezar though.
As a stat-stick. It would be more interesting if it was featured in abilities and another class could fulfill that, since necro is a caster.
Iknow, I’m saying one of the D3 followers started a city. I forget the Templar’s name, but he was upset over the corruption of the Templar order. So it’d be a guess to say that the Templars got sorted out and could make a return as a playable class.
None!
Just the paladin.
Did they say anywhere sword and board was going to be the weapon choice for the new one? Necros can do that already if they want.
What classes has Blizzard never done?
Just brainstorming. Heh. Trying to stave off a migraine despite the beautiful weather.
They never said this. They only said that they have opted to bring in a new class for THIS expansion. How did you make that read? 
As to what the next class will be though, I suspect it’ll be something like an Amazon/Shaman hybrid with spears and nature magic of some kind, probably more life-attuned. I’m honestly less interested in that than I am in seeing how they expand the existing classes though. Also, I suspect that the expansion which gives us the Diablo fight will be the one that brings us our Holy Warrior, whatever form the class may take. 
My idea for a new s&b class would be a “Shield Maiden”, although that is gender restrictrive, so they would need a gender-neutral name. But some sort of mix of Amazon and Paladin.
Using sword and shield, 2h polearms, and a new weapon type “Javelin”, usable as a 1h piercing weapon with shield, but also throwable. Skills element would be Light or Holy. Some group buffs.
Spear and shield a la 300 except in plate since barb has the visible nipple aesthetic locked down.
As a pivot, he can use 2H lances or polearms. I don’t think we’ve ever had a true spear / polear class.
I know, it would be just weird after they said that but then bring Paladin/Crusader back for some expansion after VoH. Therefore I think they need to change it somehow, but the class would be still “sword and board” (maybe holy, maybe not) since it seems that SnB is the most important aspect about the class that players want.
I also thought that a class in the vein of Cathedral of Light’s Knights (they wield spear and shield) would make a great addition.
Yeah, that would be similar to Cathedral of Light’s Knights.
Well, that’s some interesting ideas, I mean, Bard has indeed not be seen yet anywhere in Blizz games afaik, but as you said, typical bard sounds too much like support class. maybe mixing it up with some rogue/blademaster for melee, or something ranged, either bow or spells would help.
Undead, I am not sure about, I mean we already got the Necro to dabble with the undead, don’t see use of making the char himself undead. Also, we already have season mechanics in that regard, S1 we fought undead and used their powers, now in S2 we got vampiric powers.
Demon human hybrid definetly sounds cool, even if we just take the Demonhunter from WoW as a baseline, I mean dabbling with demonic powers and able to transform into a demon for some time.
Spellstealer - That would be another great choice for a s&b class, I mean a battlemage that is tanky (but more by magical means, maybe dodge, special DR, than pure armor). Flinging around spells and empowering his melee attacks with elemtal effects. Elementally imbued thorns would be nice. Having some sort of stealing spells/siphon magical energy from enemies.
The more I think about these two the more I want to play one, esp the Spellstealer Battlemage type.
a la Sparta ftw.
i can´t wait for Titan Quest 2 to mop the floor with this ip´s husk if d4´s clowndevteam is to remain. and pos.
Spellstealer/Spellbreaker, probably something like that
I mean if I were guessing previously and knew it was a new class and nothing existing would say Inquisitor or Dark/Seer (half & half, empower my attacks reduce other’s or render some targetted debuffs)
But since people are saying it may be a S&B class then I’d imagine one of those anti-magic your power belongs to me now kinda types 
Rune Knight like Celes from FF6.