*****SEVERE WARNING*******
THIS REPLY IS FULL OF SPOILERS OF THE WORST KIND
I don't know of Brightlord Davar's knowledge, but I suspect that:
A. Navani is a Soulcaster
B. Firespren make fire, Windspren case winds, etc.
C. Earth might have existed
D. Dalinar will soon become a Windrunner
E. Szeth will soon die
F. We are missing much of Surgebinding
G. Voidbinding does not use spren. What then?
H. Kaladin will acquire shards
I. Shinovar has normal seasons
J. Szeth is truthless because he was bonded, not because of his shards
K. We found the magical triad, but where are the sixteens?
L. Shards, Fabrials and Voidish magic (along with old magic?) don't work in Sinovar
M. Voidish magic might be related to the old magic
Rationale:
A. Jasna and Elhokar are Soulcasters. What have they in common with Shalan? Passion. Navani is both their mother, and is very passionate.
B. When we say the opposite, we give the scientific explanation from Earth. But look at the seasons! They are NOT right, they are completely RANDOM! Also, if the sun is up for 12h (therefore down 12h) and each moon up 4h (therefore down 4h), they MUST be up at DAY, TOO! That is never mentioned, presumably doesn't happen. What's up with THAT? Makes no sense.
C. Humans are everywhere (created by the once-human shardholders). I know, very poor rationale, and a poorer theory, but it seems the place where Adonalsium shattered or was or something. Especially when you see Shinovar and the strawberries and chicken and all that.
D. (+See E&H) Syl likes Dalinar now, and he is honorable and all that. It increases chances that he will be bonded be an Honorspren. Plus, Szeth is assassinating him, and he, Adolin and Kaladin are too important
E. (+See D&H) It has to happen sometime, Dalinar, Adolin and Kal are too improtant, Teravangion can't die and won't give the stone.
F. Aren't there supposed to be two Spren to each radiant? What draws each Spren? (Symbolheads (Passionspren?) seem to search passion and want truth, Honorspren seem to search honor and want humanity, what else?)
G. Spren are of Honor, Void is of Odium, the two are enemies. I suppose the Voidish magic is the old magic
H. (+See D&E) He can, and Renarin is still waiting for his.
I. It is, supposedly, a model of earth.
J. He wouldn't have been bonded if he was a shardbearer, the shards have been given to him by the Shin
K. (+See G&M) Spren magic (Radiant) - Stormlight magic (Fabrials) - old/Voidish magic (?)
L. (+See C&I) Maybe the moons and night could be different, too?
M. (+See G&K) Kolo?
Sources:
A. Elhokar mentions (at Adolin's duel, during the dandelion era) that he sees, in mirrors, assassins with twisted heads of symbols, a very specific Symbolhead description.
B. The only set season is the wheeping. Read Kal's flashbacks
C. The other cosmere books
D. The freeing of the bridgemen
H. The flashbacks - Kal does kill a full SB
J. Syl's Shard-hatred
All Other Ones: General knowledge/Logic
Kolo?
Critics (especially constructive ones), thoughts and responses are welcome.