I would assume "Gravity," "Vultures," "In Repair," "I Don't Trust Myself" and a few others were written after he started playing with the Trio, while stuff like "Stop This Train" and "Dreaming with a Broken Heart" probably came before.
I think In Repair he did in a few days or something and I'm pretty sure he made it with the trio. I remember watching a documentary on the making of that song.
Completely speculating on the title and art, I'd say we're 100% in for something Dead-influenced. Hope it's a jam, though most of his 1st singles are not my favorites.
God damn that's a good solo. If the album has that level of swagger and a Continuum theme, it could be one of his best.
Looks like he's facebook premiering at 4:00PM EST, though I don't know if it will be anywhere before that.