Wait, so wasn’t the implication was that in this other world, John died as a teenager because Mary never brought him back? Because Bobby hadn’t heard of Sam and Dean Winchester, so he hadn’t lived long enough to kill children, and if John died 40 years ago as Bobby said, that’d put it in the 1970′s. (Unless Bobby was rounding and John died in the nursery in 1983 instead of Mary and this world’s Sam and Dean went by “Campbell,” but Bobby never mentioned Mary having sons, either.)
Because if Sam and Dean were never born in that world, the one Mary and Lucifer got sent to... that means Sam and Dean weren’t around to kill Azazel, Alastair, Lilith, Ruby, Abaddon. Bobby and Rufus are still alive, so the Harvelles (Bill included?), Pamela, Pastor Jim, Caleb, Gordon, Charlie, all of them might still be kicking. And most all the angels died because they got involved in working with/against the Winchesters, so they might be active too. (ANNA REAPPEARANCE! ANNA REAPPEARANCE!! GODDAMMIT SPN STOP TEASIN ME AND GIVE ME BAMF COOL-ASS ANNA!!!)
Whiiiich - assuming those characters haven’t been killed off in other ways - leaves Mary trapped in a world full of powerful players, including her own murderer, and Lucifer reunited with a world full of his strongest and most loyal demons - and quite possibly Lucifer-worshipper Uriel, who’d kill to recruit more angels to Lucifer’s side.
... I like. Bring back all the cool characters, baby! I’m diggin’ the potential for S13!