Anyways, I was also thinking about Thor. I'm less certain after seeing some of the more recent solicits that this is going to happen, but I originally thought Thor was actually going to die (only to shortly return to life). For one, it cheapens the prophecy that he's been running from if he doesn't die. There's also the old Norse Myth about how Odin hung himself from a tree for nine days, travelling in and out of death, to gain wisdom. Thor has shown himself to seriously need some wisdom, and a sacrifice would tie into him filling the role of All Father. There's also the whole Loki being allfather thing that Raye mentioned.
So, how I figure this would happen is that Thor and Loki plotted something together last time they talked (the scene cut away, so we don't know what they discussed). Thor would tell Loki the prophecy and ask how he could avoid it, and Loki would be like, "Hmm, it's probably just easier to die and come back from the dead." Loki has cheated death many times himself, so this would be the perfect place for him to intercede. Maybe both of them have to do something to make it work, and Loki gets tempted to renege on his side of the bargain once he becomes All Father, only to show how he's changed by going through with it.
However, I'm not sure why Thor would bring an army with him to fight Thanos if he planned on dying -- it seems like it would needlessly endanger people. Also, the fight right now is solicited to take several issues, meaning the fight should be impactful. I just don't know if the pacing works out. Maybe Loki suggested a plan and Thor hated it, so he's determined to still try to fight his way to victory (which has kinda been his whole problem).