Sorry -- what is difficult about this?
preserve the timeline as-is -OR- don't preserve the timeline as-is
Fast-forwarding doesn't render these mutually exclusive options suddenly consistent with one another. The issue comes down to whether the existing timeline becomes a "Legends"-like repository of information, which FFG can potentially weave into its own fresh continuity, or whether FFG adopts the existing timeline.
For a writer, the question "preserve the timeline or not" is largely an empty question.
Ultimately, the only "timeline" events that matter are the ones that directly lead to or affect the story you're telling. Anything else in the timeline is fluff you mention in throw-away references to give depth to your setting.
And as a result, the only time you even care about changing or not changing the timeline is when it prevents you from telling the story you want to tell. Which is usually because you want to use characters in a way that would be precluded by the old timeline. Otherwise, the timeline is just reference material.
So, in short, the question you're asking is irrelevant, because changing the timeline is not a primordial setting decision - it's a tool they can use if and when they need it.
The relevant question is, what kind of story does FFG want to tell? .
Edited by Himoto