I wonder if Sark will react to Allison's death the same way Sloan did for Emily's or Dixon for Diane's. Think he will loose his control and go on a vengeful killing spree? He seems a little more cool-headed than that, and they also haven't built up their relationship enough on the show.
And Sydbristow, if the show really is 2 years in the future (which i think it may be, but for the sake of the rest of you Vaughn fans out there who are still trying to rationalize it away with dreams and time machines, ill use the word "if") then I would say Sark definitly knows about Allison's death by now.