Hopping onto this revived thread with my thoughts.
Meta-wise, I really don't think B$ would pull another similar shard moment with our SA shards. As I'm thinking towards the end of the cosmere, it would be really great to have a meeting of all the Shards (either virtually calling in to communicate with each other) or as a final showdown. It would be interesting to me if it's still a group of 16. Since we know one person can hold two shards, it got me thinking as my brain wanted to fill in the gap of a shard, what if we split a shard into two shards?
What if Odium loses the challenge: His backup is to do whatever is necessary to break out of his bonds keeping him on Roshar. By committing self-splitting ("split-puku"? "Sui-split"? Name pending) he gets out of the technicalities limiting him by becoming Passion and Scorn. Now free of Roshar, but split apart, one of these semi-shards seek to reabsorb the other's Investiture, while the other attempts to flee.
I seem to recall Brandon saying a splitting of a shard into two with different intents is possible but as of now it is unclear how it could happen. It would be a wild ending to Stormlight though. Either SA5 or 10.