The act of Kilik fighting with Grøh, in and of itself, does not diverge the timeline. It's one of those hidden truths of history that the trailer quote alludes to
Dude, that in itself is a divergence. Then again, you did say that they could return to the SCV era... when we all know that's not going to happen.
But the problem here seems to be your definition of divergence. A small and/or mundane detail being different from the original is not a divergence, but a deviation. To diverge means to go off in a new direction, to change the course, to do things entirely differently. Adding new things we didn't see before is not diverging, unless it alters the events that we did see before, which all signs point to that not being the case, so no, we're not diverging, it doesn't seem like.
It's a reboot. It's new timeline. Get over it.
etc etc
This all just seems like this whole debate is rooted in an argument of semantics. Whether something diverges or deviates - and the definitions of those terms - is somewhat irrelevant. We ultimately must decide if any continuity changes will be relevant? This is something we won't know until we play the game. And even if continuity changes, that doesn't necessarily entail a separate timeline than what the series has been.
SC6 can change past continuity and have it still be considered of the original timeline/continuity, aka a retcon.
SC6 can change past continuity and have it develop into its own continuity, separate from the previous games', aka a new timeline/continuity.
SC6 can just show things that the viewer/reader was unaware of that happened, and not technically change past continuity, aka uhh, retroactive exposition? "rexpo"?
We won't know any of these until we play the game and possibly until we see how SCVII pans out, story-wise. Granted, the SC wikia already has it determined to be a new timeline, so...they must be right! ^_^
But in all seriousness, what matters most here isn't even what happens in the story. What matters most is simply how Project Soul defines it themselves. As a comic reader, this issue and discussion comes up all the time. But at least it's almost always clarified by the publishers. In this case, an explicit statement from Project Soul would be cool. But there could be a variety of reasons they haven't fully indulged us how SC6 effects/changes the existing continuity.
Plus, I don't like the term "timeline" to begin with, when dealing w/ fictional continuities. It implies distinct separate ACTIVE universes (i.e. a multiverse, since timelines can be parallel, even after splitting from another), when it's usually actually an entire universe replacement (i.e. an "original timeline" never existed, no need to consider it its own timeline). Unless it's explicitly stated that they are actual separate timelines and not just one continuity wholly replacing another (which may sound like the same thing, but more on this later).
Also, I guess I never actually answered OP, tho, and I like to, even if it's late. I pray to GOD if this is a case where it is separate, unique existing continuities and a character - Algol or anyone else - is aware, then just ugh... I always feel like that's such an uninspired cop out. Again, I much prefer a real reboot w/ SC2-5 never having happened and start w/ a fresh, new take on the SC story, while still maintaining the core elements of the story.
And before there're any questions/debates on this perspective of timelines/continuities, I'll try to use examples we can be familiar with, being in the same medium - video games!
Mortal Kombat 9 - was a narrative soft reboot at first, retelling the MK1-3 story w/ some small changes, until Raiden decided to hard reboot it at the end and wipe away a vital story element (via time travel), causing a new "timeline" that was vastly different from MK4 and beyond. However, the old timeline of MK4-A still "exists" in the sense that it linearly still happened. And if you believe in the multiverse, you should believe that universes' identities can be defined by time, therefore making the old, wiped away timeline still "reachable" by time travel, multiverse travel, etc. The old and new timelines are still part of the same linear continuity.
Tomb Raider - the 2013 series was a hard reboot, a complete change in Lara's (various) previous continuities. Changes in her origin, changes in her family history, changes in her adventures, changes in the dates, changes in her look, attitude, age, etc. Not just big retcons, but a completely hard reboot. The previous continuities ("Original" and "Legends") simply did not exist, never happened. They aren't "separate timelines", but rather they just DON'T EXIST as any part of the current Tomb Raider continuity. The Tomb Raider continuity starts at the 2013 game and the 2013 game alone.
I much prefer the Tomb Raider model of continuity, or "timelines", over MK's. A fresh, true reboot/replacement of continuity, rather than separate timelines set in the same continuity. Neither of which are necessarily dependent on if its a soft or hard reboot - how a continuity is rebooted and how timelines are related to continuities are not mutually dependent.
Hopefully this is as good as it gets for my perspective, b/c this took way too long to type and I don't want to have to do it again. :)