It seems as if the First Blade is doing a lot more for Dean than making him bloodthirsty. He's morphing into some sort of a jawbone wielding superhero with whip-smart witticisms.
I'm all for a powerful, funny and sexy Dean but being strung out on First Blade juice isn't necessarily the way to go. Maybe he can hit the gym or do a couple of shows at the local comedy club to keep himself sharp.
Sam gets more concerned every time Dean picks up the blade, and since we saw the darn thing can run home to daddy's hand, what are the odds he'll able to go anywhere without it?
My bet is slim to none. Besides, if they're going to help Castiel with an army angel problem that involves Metatron, why not have it along if slaying the little weasel becomes an option?