I don't think Cas would have fulfilled his episode number quota by April 15th. Besides that one site says Misha's signed on for season 6, so I assume he's probably safe. I hope. ::crosses fingers::
I'm really worried about Bobby though, but he doesn't really go into the fight much anymore since he's wheel-chair bound.
Important character doesn't necessarily have to mean the core four (hehe that rhymes) characters. It could very well be someone like Chuck. He's a very important character because he's the prophet. But Cas died before at Raph's hands and someone brought him back, so it's possible that this will happen again. I noticed it didn't say "will sacrifice himself", it said "themselves". Could this be the ep where Dean and Sam die and go to Heaven or whatever?
In the same respect, I guess you could consider Gabriel a very important character cause in the grand scheme of things, he's important since he's an arch angel. He's the only arch angel that would even come close to possibly being on their side.
Could also (but doubtful) be Crowley. :lol:
The only other female character that I could think of that might sacrifice themselves would be Missouri, but I don't think it's her because we've only seen her the one time. But then again, it does say that we'll see characters we never thought we'd see again.
I think that this sacrifice will not be permanent. Notice that it says after the sacrifice part that crises will come to head for Dean and Cas. Not Dean and Sam, but Dean and Cas. The way that's worded makes me wonder if it is indeed Sammy who sacrifices himself. Let's think about it for a second. Dean has sacrificed himself for Sammy and gone to Hell for him. Maybe Sammy will return the gesture. Maybe what Lucifer said about Detroit will come to pass. Maybe Lucifer will tell Sam that saying yes is the only way to save Dean. Maybe the reason that Lucifer is so sure that Sam will say yes is because of Sam's love for his brother. I mean Sam loves Dean more than anything else in the world. There is no doubt in my mind that Sam would sacrifice himself if that meant saving Dean.
The "suicide mission" part could just be that the whole mission would be suicidal for all of them and that's another reason why Sam feels he has to say yes... to save Dean (and maybe even Cas).
Or its possible that one of the boys will sacrifice their own life knowing that they'll be brought back. Dean's sacrificed himself for Sam before and would do it again in a heartbeat. Sam would give his life to save Dean.
I really think this could be about Sam saying yes. Remember when Dean was sent to the present and was told that Sam said yes, he couldn't figure out why Sam would do that. He thought it was because of their fight which is why he made an attempt to make up with him as soon as he was back in the present. But, what if the real reason (even in that crazy future) that Sam said yes was to protect his brother? Maybe this is the episode when Dean finally learns why Sam said yes.
I can just picture Lucifer trying to get Sam to say yes while his minnions have a hold of Dean (and possibly Cas too). And Sam saying "if I say yes will you and your followers leave Dean (and Cas) alone and not hurt him/them?" And Dean saying, "Sammy, no!" with tears in his eyes. And Lucifer telling Sam, "I give you my word that no harm will come to him/either of them at my hands or at the hands of anyone under my command". And Dean again yelling, "Sammy, no please don't do this! We'll find another way, I promise!" And Sam looking at Dean and saying, "You went to Hell to save my life, Dean. Its time for me to protect you now." And Dean crying and saying "Sammy, I don't want you to do this." And Sam saying, "I'm sorry, Dean, but I don't think I have a choice." Then Sam turning to look at Cas and saying, "Cas, please take care of Dean for me." And then walking off with Dean continously yelling, "Sam, no!" And Sam saying yes to Lucifer. And then Lucifer in Sam blinks both Dean and Cas back to Bobby's or a motel or whatever.
Then the rest of the season would be Dean and Cas trying to figure out how to get Lucifer out of Sam without harming Sam.
Or possibly since its in Dean's family's bloodline according to Michael, maybe Sam will ask Michael to take on him as a vessel and that he'll kill Lucifer. Boy would that be a twist.