I'd wager 99.99% that all the people who are shown to be "killed" during Blackest Night will come back at it's end. Too many upper/mid tier characters are being knocked off for this event. I'd also wager that some of the deaths we've seen prior to when this event is supposed to take place (Dolphin and Cerdian come instantly to mind, Kid Devil/Eddie too) were killed just because Johns planned to use them in Darkest Night.
I always think there's no way (especially now with Diane Nelson there to make sure the DC "Brand Name" characters make money for the WB) that Aquaman and Martian Manhunter stay dead. On the other hand, the Graysons and the Drakes are obviously not going stay alive, nor are some of the characters who have legacies DC wants to push already active (I'm thinking of the older JSA crew in particular). But, I wouldn't mind seeing Ted Kord back or the Dibneys (outside of three issues of the Outsiders DC never did anything with the Ghost Detective thing) and if this does lead to mass resurrections I wouldn't mind.