Well, quite honestly this is where The Matrix would come into play. How do you know this world is real? The question is briefly brought up in the DS9 episode, "Trials and Tribble-ations". Granted it took place after GEN and would probably be a reality where Veridian III was destroyed (if we go with your theory which I partly agree with). When the Department of Temporal Investigations grilled Sisko on his journey back in time, one of them said, "For all we know we could be living in an alternative reality right now." They brought up a point we will never really know the answer too.
Now, I'm sure if we ask Brannon Braga or Ronald D. Moore wither the timeline really was restored and Picard really did save the crew of the Enterprise, they would simply reply with a "yes." I'm sure at the time they were just really excited to be writing a Star Trek story for the big screen that they didn't really stop and think about certain aspects. But to remain in universe, I believe that the timeline really was restored. Now, as far as Soran is concerned, I believe he is still in the Nexus.
*The word "dabo" means "I will give" in Latin, and "Gold" in Aramaic.
J.J. "Binks" Abrams is taking over sci-fi!