Why I think Castiel will sacrifice his grace for Dean and die in season finale

The fandom has been going nuts and speculating vigorously about the season finale, especially after spoilers and extended promo.

Here are my thoughts as to why I think that Cas will give up his grace and meet his sorrowful ending:

1. The season title. It’s angel grace banishing the demon smoke/darkness/evil. I believe the show gave us a big hint/foreshadowing there. And I know only one angel who would  willingly give it up to have Dean cured.

2. Castiel’s grace was hidden in a book called The Ingenious Gentleman Don Quixote of La Mancha, written by Miguel De Cervantes (if you have not read the book I strongly recommend you do it!). In the book the main hero Don Qixote travels together with his friend Sancho Panza to fight against the imaginary evil, getting in lot of troubles. While it’s funny, it’s more tragicomedy, especially in the end. I think the writers made a perfect choice there, because this book fits Castiel perfectly.  And I have a feeling that it was a foreshadowing once again, probably telling us how sad Castiel’s ending will be. 

3. Robbie Thompson’s tweet. “Pizza party or last supper?” Well, Guess what? One of the people sitting at that table is already dead. Maybe it will be Cas’ turn soon?

4. Misha’s words

5. Jensen’s words:

Also: Jensen said that Sam would be the one doing all the crying in the finale. I can’t find the source right now, so if you have it, drop me a PM and I will add it. Now, let’s think about it: Dean cannot die as the mark will not let him (unless he gets rid of it and THEN dies) but he died in last season so I don’t think it’s him dying AGAIN. Then, I am pretty sure Sam will not cry over Crowley as he promised Rowena to kill him. I don’t think they would make it so big if it was Crowley. I mean, yeah he is a great character but all the fandom knows that sooner or later he would die and kind of got used to this thought. So, who do we have left? Of course Cas! Now, Cas’ death would hurt like hell and that’s probably why they described the finale as emotionally traumatizing.

6. According to Misha, the finale will not only “deliver,” but it will leave viewers with a serious case of whiplash. “There’s going to be a moment when everyone breathes a collective and triumphant sigh of relief,” he says, before ominously adding, “followed by a horrific ‘oh shit’ moment.” Translation: The finale will probably make you cry. all (source)

This is all I can think of at the moment. If I remember anything more, I will add it.

Also, I hope that I am wrong. I do not want Cas to die (though probably he will be brought back).