I still think Crossbones works best as Skully's hench, so I could def see him returning for a Red Skull redux in Cap 3 (or even Avengers 3). But not much of anything else. If TA2 is about Thanos, as most fingers point to, then Brock is hopelessly outclassed and would have nothing to do in that cosmic throwdown except die like cannon fodder. Maybe an Avengers that features the MoE, I could see.
I want something good to die for, to make it beautiful to live.
---- Queens of the Stone Age, "Go With the Flow"