Exactly, it was following up on what Lovok said in "The Die is Cast": With the Tal Shiar and Obsidian Order out of the way the only ones left to deal with would be the Klingons and the Feds.
And what happens at the start of the next season? War between the Feds and Klingons.
Martok was replaced two years before "Purgatory's Shadow" meaning it happened a little before "Die is Cast". That's probably when most of the major infiltrations happened (except Bashir).