Stomlight/Mistborn era 1/2 spoilers in here.
Had this theory stewing for a while and wanted to get it off my chest.
Disclaimer: I'm not fully up to speed on all WoBs/interviews and the main theories present from people. I'm also not going all out with finding quotes here, though I'm pretty sure you can do that.
So, the basis of my theory is that either era 4 or the back half of the stormlight archive will focus on a shardic conflict between the shards featured in Mistborn and Stormlight. Where all the shards on each side are combined: Honor, Odium, and Cultivation against Harmony and Autonomy, setting up a set of novels where there is no true 'bad guy' - both sides involve people trying to do what's best.
Let's take the Scadrial side of things first. We know Harmony has issues taking action, and era 3 will likely in some part involve him morphing into Discord. The main conflict will probably be with Autonomy. I think the endgame here will feature a solution that says "Hey, ya know what might help Harmony/Discord deal with not being able to take action, or taking too much action? Let's give him a little Autonomy!" Which sets up a nice play on words - what do you think you could call a nice, harmonious version of Autonomy? Freedom! In the end, my guess is that era 3 closes with (hopefully) Sazed being a vessel for all three of Ruin/Preservation/Autonomy, and being named Freedom. Scadrial will, thus, be primarily oriented towards letting different communities in the cosmere be free to grow on their own.
On the Roshar side, meanwhile, we already know what the combination of various parts of those three shards takes. We know Honor/Odium would likely be called War or something to that effect (in sprit at least; the names of the lights don't necessarily directly translate to shard names). What could War + Cultivation be? I'm going to go with Society, or Civilization, or something. The fact that Dalinar continuously gets told to Unite them can come into play too. The 'Them' in that quote continuously gets expanded - and there's no reason it couldn't continue in that way. In the end, I'm betting he unites the shards of Roshar themselves, and in doing so unites all their people's. Which sets Roshar up to be a group more focused on creating a big tent, and interacting with other worlds and such more to bring them into the fold themselves rather than letting them grow and develop alone.
Which really sets up nicely for a conflict between Roshar and Scadrial where none of the people are bad, and each side has the powers of three shards. One side wants to unite and bring people together, the other side wants to let each world have freedom to grow and change by themselves. Us readers will have sympathies on both sides, having been a part of both mentalities development, and neither side is truly wrong, setting up a very nice final conflict.
(As an aside, I'm not sure how or if other shards like Devotion/Sel and such play into this).
TLDR: Harmony/Discord + Autonomy = Freedom, Honor + Odium = War + Cultivation = Society/Civilization. Final conflict: Freedom vs Society.
