This started as a totally random question, but I realized halfway through it this could maybe lead somewhere interesting (just in terms of random fan talk, not where the show would go realistically). If we assume time travel leads to parallel universes, then the universe with Weather Wizard's tidal wive still exists, right? Except, by traveling through time, Barry left it. He left it before fully stopping the tidal wave, so it likely hits. The last thing that Iris would have seen was Barry disappearing into a wormhole. Joe has a broken leg and is Weather Wizard's prisoner, so he's likely dead too. Cisco was killed by Dr. Wells, whose identity has been revealed meaning Caitlyn is likely next.
So in essence, our five main characters (on the hero side anyway) are gone, but our main villain is now trapped in the past, alone, and with no Flash to stop him from doing whatever he wanted, and if he couldn't get home, the alternative isn't all that appealing. Unless Wells saw fit to do so, there would also be nobody to stop any of the other metahumans or non-powered villains in Central City either.
Of course, there is a fairly notable meta human from Central City who's unaccounted for. I'm willing to bet Ronnie Raymond would want some answers if he heard that Caitlyn (and, for that matter, Cisco and Barry) were suddenly either dead or totally unaccounted for. Between he and Professor Stein, I'm guessing they'd eventually be able to put two and two together and realize some level of involvement from Dr. Wells. In other words, we're headed for a reckoning between Firestorm and the Reverse Flash, and considering how badly RF kicked his ass when he had Barry and Oliver on his side, I think it's fair to assume Thawne would get the best of Firestorm and kill both Ronnie and Stein.
Now let's broaden our scope a bit. No Barry means Oliver and Malcolm don't have a deus ex machina "get out of Nanda Parbat jail free" card, meaning (even with the butterfly effect, I think we can reasonably assume their plans would have been roughly similar) there's no Ray super cure to save Starling, so it is destroyed as well, and even if Oliver manages to still kill Ra's al Ghul and save himself, not to mention drag himself back to Nanda Parbat to free the others, they'd have no home to return and no one to blame but themselves. Even if Oliver still wears the hood on his own, I can't imagine Team Arrow making it through that in its current state, so there goes our other major hero and his home city with him.
Going even further, with no Barry, no Team Arrow and no Firestorm, there likely are no legends of tomorrow. That means Vandal Savage's plot likely goes unchecked, or at least checked by someone else (Malcolm's LoA?). Damien Darhk is still out there with whatever evil plans we'll see in S4 of Arrow. The League of Assassins is still a threat in some way, whether it's with Ra's (who kills Oliver in this scenario), Malcolm (who Oliver, for some reason, still gives control of the league to even after they fail), Oliver (maybe watching his city die changes him) or no one giving commands, putting a lot of freelance assassins on the market to be scooped up by god knows who. Oh, and there is the literal 800 pound gorilla in the room who happens to have telepathy and is lurking in the Central City sewers, getting smarter, no Flash to throw him in front of a train. Two major American cities are either destroyed or are in the hands of the criminals. Their heroes are scattered, broken and dead. And looming in the background? A certain "crisis" in 2024 that causes the red skies associated with a certain multiversal villain that has a history with the Scarlet Speedster. So... yea... this is one dystopian universe.
Here is the eventual point I promised. Now clearly, it seems like Barry does not intend to go back in time and save his mom. Therefore, if Flashpoint were to happen, that probably isn't what leads us there. In truth, we probably aren't getting a directly Flashpoint storyline. But here we have a dystopian universe, one created specifically because Barry Allen disappeared. We could either have a dead arrow, or a live one that's been changed greatly from what we've seen and perhaps becomes more volatile and willing to kill (not unlike FP's Batman). We have two decimated cities and multiple large, evil groups that might like to take advantage of that. We have nearly every villain still on the board and a hero vacuum that might create a new "lead" hero like Flashpoint's Cyborg, maybe Ray Palmer, maybe someone else. We also have a world that would deeply affect Barry if he ever got to see it. A universe in which everyone he loves is dead and his home is under siege, all because he's not there. I don't know what machinations it would take to get Barry there, I don't even know if it's possible, and I might just be saying all of this because I realized while writing this how fascinating this world would be, but if the writers ever did decide to do something resembling a Flashpoint storyline, this universe is up for the challenge.
t:
yeah its better that way i think ...but i will tell you it was AWESOME!!
