-The dilithium being red in the opening credits.
-The wormhole (also in the opening credits) and the mentioning of the nearest one by Booker, whose face began to glow a bit like Dukat's under their influence, when he used his powers.
-The prophecy in DS9 about a golden age for Bajor lasting for a millennium.
-Dukat talking about the Pah Wraiths *burning* across the alpha quadrant.
-The connection of the Prophets and Pah Wraiths to time and their perception of it, which might be relevant to the outcome of the temporal (cold) war.
-The possible return of Dax
-The bajoranlike looking new combadges.
-Season 2 starting its arc with the first appearance of the Red Angel, while the first episode of Season 3 introduced Booker.
-The name of the cat being Grudge

By the way, i'm not sure if Grudge's supposed to be a real cat or something else...