people are talking about how a mindwipe is such a lazy option for John not knowing Mary is a hunter, and I AGREE, and i am also 98% sure it's not going to be a mindwipe - at least, not between 1972 and 1973. So while we don't know if the show is going to do the 4.03/1973, this whole post is gonna assume that they are.
Though the idea of John going through repeated mindwipes is hilarious, it is kind of lazy, and Robbie Thompson, our FRIEND, isn't lazy. He's fun, he's innovative, he likes a loophole. So I found one for him.
Why do we assume that in 1973 John doesn't know Mary's a hunter? I allowed myself to puruse the episode. The only evidence I can find that might imply that is Mary saying:
MARY
Okay, wait. There's things you don't know about me, John.
SUSPICIOUS! Is what I would say if I haven't read the summary for SPNWIN, which says:
But secrets run deep for both the Winchesters and Campbells
Secrets run deep? Deeper than hunting, mayhaps? This isn't the only thing that leads me to believe there will be no mindwipe between the years, for example we have no actual proof that John doesn't know about hunting. Him being confused about Dean asking about sulfur and cold spots might just be because this random stranger that may or may not be stalking him is asking him weird questions. During the diner conversation with Mary, he just offers to talk to Mary's dad about their relationship. Samuel implies during the dinner with Dean that he thinks John is a civilian, which could just be the cover Mary and John used because John is a Men of Letters and they're notorious for not liking hunters. And that's basically it for John not knowing about hunting things. There's actually a scene that leads me to believe Robbie might incorporate:
MARY runs up to JOHN and throws herself into his arms.
JOHN
Hey, you – you okay?
MARY
You promised you'd take me away.
Mary in the prequel wants out. She wants to leave the life. Maybe John promises to take her out of it? Come on, it'd be cute. See the country together.
Then again, I have no idea what's going to happen. Jensen said it'd be twists and turns to arrive at something instead of using the straight road. I'm excited.