User blog comment:LilyheartsLightning/Citadel and Reckoning DLC announced/@comment-4782844-20130223190909/@comment-1679409-20130223195506

That's a good question regarding the replacements. No only can Wrex be dead at that point in the game, but so can many of his logical replacements (Wreav, Grunt, Dagg, Eve). Ditto Mordin (Padok Wiks and Kirrahe may be dead at that point). This kind of makes me wonder if the number of squadmates you interact with is limited (i.e., if you interact with, say, Samara, you don't interact with Jacob) or if they just won't put replacements in (a la Kasumi's ME3 mission).