So how many here are on the "there's no multiple timelines (outside perpetual world loop), just Zack and Biggs adventuring in the lifestream refusing to move on, soon to be joined by Aerith" -theory train?
There's just bunch of stuff the devs have said & what we've seen in the trailers that would really fit nicely with this interpretation. Particularly the ever present comments about not changing the big picture of the story and this bit about Zack's role from recent interview:
Through [the character of Zack], players will be able to experience and understand more of the Final Fantasy VII worldview and it will deepen their understanding of the Final Fantasy VII world. We've used Zack to depict the combined view of Nojima, Nomura and Kitase - the original creators - intent of this world of Final Fantasy VII came to be and its policies and rules governing this world. This is going to be depicted through the character of Zack. As much as the Whispers within the story, Zack is an equally, immensely important, crucial, key character to this story"
It's just so hard to imagine what Zack's journey in a completely random mishmash timeline with random events could teach us, whereas if it's about being inside lifestream and learning about it (and maybe Sephiroth's influence there too, he is after all a self proclaimed "traveller of the lifestream"), it suddenly makes a whole lot of sense.
This video summarizes the position well:
Finally, I was reading through SQueenix's press release materials and it said this about Biggs:
NEW CHARACTER: Biggs
After surviving the fall of the Sector 7 plate, Biggs awoke to find that he is the last remaining member of the illfated anti-Shinra rebels, Avalanche. Having recovered from his injuries, he now seeks revenge against the company that murdered his comrades.
So Biggs is supposed to be the same Biggs who was involved in an attack to defend the plate, together with Cloud et. al. ? While now hanging together with Zack who's hauling around mako-poisoned Cloud having just arrived in Midgar (which supposedly happened at least months before the whole platefall business) ? Nothing adds up... except it's the lifestream.
Finally, something else I noticed about the press materials & the alleged spoiler/leak posted above:
In the press releases, there's a bit about the "protorelics":
Protorelics are artifacts of unknown origin that emit a unique energy signal. These elusive antiquities are hidden throughout the world─butwith the aid of activated remnawave towers, Chadley should be able to point you in their direction. Be warned, however: they seem to alter space-time, and are known to cause strange phenomena.
This is pretty strong corroboration to the leak if you ask me.