Dragon Ball Super: is the Super Saiyan God prophecy a plot hole?

There is a plot hole at the heart of Super Saiyan God that I had never picked up on until my friend TZ brought it up in a discussion. The Oracle Fish's prophecy that sent Lord Beerus to Earth was made before the timeline split, yet in the original timeline Goku could not have been alive to fight him. I've looked at a couple of ways to explain it, but I think the easiest answer is the right one: it's a plot hole.

The problem sits in Battle of Gods, the story told both in the Dragon Ball Z: Battle of Gods film (2013) and in the Dragon Ball Super anime (2015).

Battle of Gods takes place in Age 778, and Beerus woke for a prophecy made in Age 739

According to the official timeline of Dragon Ball Super, the events of Battle of Gods take place in Age 778, in both Super and the film. Beerus woke up on that day because he set his alarms for it. That was the day the Oracle Fish prophesied a great warrior would challenge Beerus in combat, and that warrior, of course, turned out to be the Super Saiyan God.

The prophecy was made to Lord Beerus 39 years before the events of Battle of Gods. Count back 39 years from Age 778 and you land on Age 739. That year is very important in Dragon Ball lore, because it is the year the events of Jaco the Galactic Patrolman took place.

Jaco the Galactic Patrolman already contradicts when Goku came to Earth

According to Jaco the Galactic Patrolman, Age 739 is also when Goku lands on Earth. That directly contradicts the originally established lore, specifically the anime, where Goku coming to Earth and Planet Vegeta blowing up took place in Age 737.

So there's already one contradiction in the dates. That's not the plot hole I'm focused on here, though. The one I mean has to do with time travel.

In the original timeline, Goku dies of the heart virus before Beerus wakes up

In the original main timeline, before Future Trunks and Cell used time machines to go back in time and split the timeline, there could not have been a battle between Goku and Lord Beerus on Earth. Goku would die of the heart virus years before Lord Beerus woke up.

If the Oracle Fish made this prophecy before the timeline split, that tells me the prophecy would have had to come true in all the timelines. So how is that possible? The easy answer is that it's a plot hole. You could use a bit of headcanon to come up with an alternate scenario, though, and there are a few worth walking through.

Theory one: the Oracle Fish was wrong, or Beerus met Goku in the afterlife

The easiest headcanon is that the Oracle Fish in that timeline was simply wrong. Beerus woke up and there was no Super Saiyan God. The only Saiyans on Earth at that point in the future timeline would be Gohan and Trunks, and Gohan would, of course, die in Age 780 of the future timeline.

That raises the question of what happened to Beerus in the future timeline. The alarms and the prophecy were set before the timeline changed, and these events would have happened well before the appearance of Goku Black and the genocide of the future gods. One theory is that Beerus possibly did wake up and come to Earth, even though there's no story of it, met Gohan and Trunks, realized there was no Super Saiyan God, and maybe met up with Goku in the afterlife.

The issue I have with that is the form itself. For Goku to unlock it, he would have had to do the ritual, unless he trained with a deity who could teach him, like Whis. Whis didn't know who Goku was at the time. So the idea of Beerus meeting Goku in the future timeline at that same moment doesn't hold up for me.

Theory two: a predestination paradox around Future Trunks

Another theory that could be possible, even though it's highly unlikely, is a grand time paradox. The idea is that when Trunks and Cell started traveling through time with the time machines in Dragon Ball Z, it created such a butterfly effect through a temporal paradox that it changed the future as well as the past.

You can look at it as an extreme predestination paradox. When the Oracle Fish made the prediction about Goku fighting Beerus, she somehow knew a time traveler would come to the past and prevent Goku from dying. That would let the timeline course correct itself, so the prophecy would come true and Goku would end up fighting Beerus.

To me that is "way too whacked out." A time traveler affecting events that happened before he went back means Future Trunks was destined to go back and change that timeline no matter what. I have a hard time accepting it, because it goes against the rules of traditional time travel stories and against Dragon Ball's version of time travel. It would mean that no matter what Trunks did, even if he never went back, Goku would have survived, which contradicts everything.

Why I think Toriyama simply forgot that Goku died

"In science, the easiest answer is usually the right one." And the easiest answer here is that Toriyama completely forgot that the main timeline Goku died, at least when he was writing Battle of Gods. Maybe, just maybe, there was another Super Saiyan God in the future timeline who hasn't been revealed yet. But I have my doubts.

I think Toriyama just didn't think it through. That's why a prophecy made in a timeline before the timeline was split is, without a doubt to me, a plot hole. That doesn't mean you can't like Battle of Gods or Super. "It's just something fun to look at."