Actual Lore about Dragonborn, and the recently tested new Dragonborn stats. Draconic Feats & spells, and a revamped take on Kobolds, from the same UA. All of the Dragon's from throughout the games history in a Bestiary. Best guess is that this will be like Volo's Guide, but "Oops! All Dragons."
Title character doesn't mean anything for monster/rules expansion books. Tasha's and Mordenkainen's weren't about Greyhawk, and Volo's and Xanathar's weren't about the Forgotten Realms. I expect Fizban will mainly be referenced in the little side notes.