It is a retcon of a preexisting canon. The story depicted here is playing out more or less similarly to Dark Forces. The characters are very obviously based on them, and bare an incredibly astounding physical resemblance to them, but have been renamed. Jyn Erso was originally Jan Ors. This isn't a feminizing of the plot either. In the original version of the Death Star Plan Heist, depicted in Star Wars : Dark Forces, Jan Ors was the leader of the operation. Though since it was a game, she took a back seat role in actually performing it with Kyle Katarn having most of the action. They haven't named his counterpart (rogue-ish guy with the beard), who looks almost identical to his EU appearance, but it's safe to say he won't be called Kyle Katarn like his Pre-Disney EU counterpart though it looks like they flipped their roles. In the game, Kyle was a former Imperial, turned criminal that was recruited in an joined with a veteran Rebel agent, Jan. Looks like this time it's the other way around. But the Jan-counterpart still seems to be taking charge. Interesting casting choice for Mon Mothma. In the original game she was the person giving Jan orders so it was crucial to include her. It's the same actress that played her in Revenge of the Sith (though most of her dialogue scenes were deleted), Genevieve O'Reilly . And since it's been 11 years, the actress has aged enough to plausibly pass for her older character originally played by Caroline Blakiston. O'Reilly was chosen for the Sith role in the first place because of how much she resembled Blakiston.
I am rather disappointed that they renamed the characters. Though I suppose it was to be expected since they renamed Jacen and Jaina to Ben and Rey in The Force Awakens, though their characters were extremely similar and did some of the same things. But I do like the characterizations this time. They are similar to the originals but a little more realistic and gritty, which is true to the original intent in the original Dark Forces game. Still it's interesting in that the second Disney Star Wars film is an adaptation of a video game.A loose adaptation, but an adaptation nonetheless. Best to not spread that though. Video game adaptations tend to be more harshly criticized regardless of how good or bad they actually are.