So last night, during Sanderon's livestream, I asked if the maximum amount of Bondsmiths is set at 3 like it was historically. Brandon responded that there have not been more than 3 at one time historically with emphasis on historically. The smirk and laughter in the background makes me think he's being coy about the possibility of more than 3 Bondsmiths in the future.
My theory is that there could be Bondsmiths for each type of light and associated "god-spren".
Stormfather - Stormlight
Nightwatcher - Lifelight
Sibling - Towerlight
BAM - Voidlight
Sja-anat - Warlight
??? - unnamed Lifelight/Voidlight combo. This spren may not exist yet or we're not aware of it.
BAM being a god-spren for Bondsmiths might answer a lot of the questions about deadeyes, the recreance, ect. This would tie in to the theorizing that imprisoning her lead to tons of Connection issues on Roshar. Her bondsmith might be able to fix these Connections but I might be getting too out-there with my theory.
Let me know your thoughts. First Topic post on 17th Shard so let me know if I messed anything up (tags, spoilers, ect)!
-Beren