It would all mostly fit in to the angels playing the long con theory (except for why couldn't the angels just fly in and take what they want, if they're after the tablet or Kevin. Though I guess that'd fit into the same suspension of disbelief that a lot of this show operates on, like how Crowley hasn't managed to kill Sam and Dean by now.)

But if it turned out that Cas was pulled out by the angels at the same time Dean was, it'd be pretty weird for Dean not to put together that Samandriel was lying to him at the auction. So I think it'll probably turn out that just some freak circumstance prevented Cas from making it through (though that doesn't really fit with the specific guilt they wrote about Dean associating leaving Cas behind as it being about him not needing Cas anymore.)

I'M JUST MAKING MYSELF MORE CONFUSED.