Based on speculation that Godslayer is rumored to someday kill Verra, it would make sense that she would be the intended target. If Verra was killed, there is a character that is already in place to take over her place as a Lord of Judgment.
Steve has mentioned that he originally planned to call Taltos "Easterner", but his editors suggested the change. is it possible that "Taltos" was originally the title reserved for the last book? It would fit the theme. It's been suggested that the title of each book relates to the way Vlad has to act like a member of that house during the book, and it's a lot easier to act like a taltos than a contract, whereas in Taltos Vlad's Eastern origins were a major theme.
Another possibility: "the last contract" may be the last contract taken out against Vlad. Okay, unlikely, but there are still an awful lot of people out there who want him dead.
Yet another: Either or both of the above plus a surprise twist ending. Author fakes us out by including a contract for Vlad, and/or a contract against him, then reinterprets "contract" in a less sinister way that's more significant to the world's fate. For example, the last contract might be an agreement involving Kieron and the gods and brokered by Vlad, ultimately resolving relations between Dragaera and the East, giving Easterners access to Deathgate Falls, or making them part of the Cycle, or some other momentous change.
Such an ending would not only give impetus and conclusion to the series as a whole, but neatly encapsulate Vlad's career arc beginning as an assassin, but concluding as a power broker and master negotiator with the gods, surpassing even his previous work as Dolivar. (Otherwise, you'd wonder why Vlad was more worth a series than Dolivar!)
Perhaps the "contract" is one of the Jenoine, or something to do with the Jenoine and an attempt by them to invade Dragaera? Vlad could be hired by the gods. Or maybe he's hired by the Jenoine to kill Verra. Not likely, I know.
Well there WAS that blank spot on the physical representation of the Cycle so I'm thinking there will be an Easterner House added and it would make sense to do it in the last book.
House Phoenix is nearly extinct. Have Easterners filled their now-empty spot in the cycle? Might Zerika unilaterally throw her House open to Eastern recruits, using the Jhereg's sale of titles to Easterners as a precedent?
There is a piece of conversation between Sethra Lavode and Vlad in the book Iorich that has stood out in my mind for a while:
"Most of my thoughts about the law involve ways to circumvent it," I said.
She smiled. "I always knew you had the makings of an Emperor."
I can't help but think this is somehow significant to the endgame for Vlad, especially considering how much foreshadowing that has happened throughout the books if dissected into chronological order. Usually the foreshadowing appears in the forms of small statements, observations or thoughts that seem inconsequential at the time until later in the story as a chronological whole.