I don't think Forrest and I will ever agree about the essense of time travel in the Maraverse, but I'm not saying that I believe that Infinity corrected the original M2 timeline either. I think that that was the interpretation of the Rubicon team, but at the end of the day in Infinity, the combined Durandal/Thoth entity released the player to go his own way. That happened after the containment of the Wr'kr, and the final Infinity timeline certainly did not cease to exist.
I don't see time as being linear at all in Marathon. In my mind all timelines branch out from a common point, the release of the Wr'kr, and loop around back to the same common point. That common point exists in all timelines and in effect none of the timelines exists as an independent entity at that single point. It's a similar concept to the idea that infinity and minus infinity, as well as the corresponding imaginary values, are really the same point, which is 1/0. In any case, the Wr'kr represents chaos and the absense of time as we know it, so all timelines truly cease to exist after the Wr'kr is released. Yes, I realize that the secret levels in Infinity take place after the release, but these are entirely outside of the space-time continuum. When the player finally succeeds in containing the Wr'kr, that timeline is the only one that continues beyond the pivotal point. In that reality, the player was abducted by Tycho after M1, fought with the Pfhor against Durandal at Lh'owon, helped Tycho destroy Durandal in Hang Brain, but then saved Durandal's core, betrayed Tycho and uploaded Durandal's core into Thoth, making possible the eventual containment of the Wr'kr. If this is really the case, then Durandal never captured the Rozinante etc. This leaves a very big gap between Infinity and Rubicon that in all probability cannot be reconciled. In WMaiD, however, Blayne is going to try.
What's the real answer? Time travel is impossible. It cannot exist within the context of our universe. Indeed, some people believe that time itself is an illusion - it is merely our own observation of the passage of events. But then we're really talking about science fiction and, in that realm, anything goes.