Yeah, it's probably is a safe bet that most of the characters who's fates haven't been established yet probably didn't make it to A New Hope.
The only ones I'm not sure about are Cal Kestis, and Cere Junda, right now I could see their fates going either way. That's one of the big reasons I'm anxious for some kind of follow up to Fallen Order, I really want to know what happened to them as they got closer to A New Hope.
So the problem I have with Cal, and this applies to Cere as well, is the same problem that Kanan Jarrus posed in Rebels. As fully knighted Jedi the break the core conceit of Luke's existence. By Return of the Jedi, Luke is the last Jedi. We can "a certain point of view" that one I suppose, but let's be fair: Yoda isn't qualifying that statement one bit. Luke is it, and it is Luke.
Ahsoka gets around it on a technicality, having left the order before she was knighted, and so is a Jedi in practice but not in name. Ezra winds up in the same space, effectively a Jedi but not quite really. And even then, by seemingly taking Ezra out of play during the OT, the Rebels creatives hedged their bets just in case. By being MIA during those events, he can be found later and still not break the conceit.
Kanan had to die in my mind. Period, full stop. There was no way he got out of Rebels alive, and sure enough he didn't. Now, his death worked magnificently in that show and felt both earned and meaningful, never like they just had to remove a piece. Cere and Cal fall into that same category, to an extent.
I do think that Cere is probably toast. Her character in Fallen Order is excellent, but the set up for a heroic sacrifice would be a solid endpoint for her. She failed to protect her padawan during Order 66, but this time maybe she gets it done and presumably it will be saving Cal.
Cal is an interesting one. The ending of Fallen Order, and some of the character interactions within it, definitely open doors for Cal to leave the Jedi path. Which could put him into a similar place to Ahsoka and Ezra. But if he stays on it? He almost can't live to the OT, or at least not to RotJ, it's the same problem Kanan had. And honestly, the conclusion of Fallen Order creates a situation where a rematch with Vader would be coming full circle for Cal. I don't know what the context for it would be, I leave that to more clever people than I, but I can absolutely see Cal's story ending with Vader's blade.