This is definitely a possibility. They may make two volumes for future books. RoW is slightly longer than Oathbringer, so that could possibly be a problem. You are remembering correctly about Oathbringer needing something different.
Yes, you do. Sorry I missed your post at first.
There's a thread discussing what you would do if you were the only person who knew Hemalurgy existed. It's interesting.
My favorite magic system is probably Surgebinding as well. If I could bring it into our world with Stormlight being brought in, I would do that one. Otherwise, I'd bring the Metallic Arts or Allomancy into our world.