I think an anti-druid of some kind is possible. 2e had a kit for it and 3e had various flavours including variant class abilities around death including getting turn undead and atleast one prestige class (blighter). don't know about 4e but that still shows a history for the archetype.
Other archetypes from past editions include terrain specific (already covered with land spell lists), anti-civilization groups, wild shape specialists (moon), animal companions (unlikely considering the issues with the ranger), swarm/vermin shapeshifters and druids that become plants of some sort.
I would like to see the last two the most as far as flavour goes, but mechanically i'd like an option between the melee speciality of moon druids and the heavily spell reliant land druids. it would probably need extra spell access for melee buffs, but subclass abilities could cover it too.