Arrow is already beginning to change the future for Star City in 2040 after this week's episode, "Present Tense." Despite traveling back in time, Mia Smoak (Katherine McNamara), William Clayton (Ben Lewis), and Conner Hawke (Joseph David-Jones) are still facing a familiar foe. The eighth and final season of the Stephen Amell-led series is tapping into the bigger comic book themes of the Arrowverse ahead of Crisis on Infinite Earths. With the Multiverse being the primary focus, the season is now exploring the time travel territory through the Star City 2040 characters. Following the cliffhanger in "Leap of Faith", Oliver and his team are getting to know the legacy that protects Star City almost 20 years from now.
After clashing with the Deathstroke gang in 2040, Oliver's children along with Diggle's (David Ramsey) adoptive son are now forced to face them in the past. Future Team Arrow, having just lost Zoe Ramirez (Andrea Sixtos) in their timeline, are determined to stop J.J. Diggle (Charlie Barnett), believing he came with them. While he leads the force in the future, "Present Tense" came with a twist on who is under the helmet in 2019. It's revealed that it's actually Grant Wilson (Jamie Andrew Cutler), Slade's older son, who is behind the gang in 2019. As Conner put it, it's a different game now with new players and new rules.
But as the future characters are getting involved with the past, the future of 2040 is already starting to change. When they first engage with the Deathstroke gang, Team Arrow ends up saving them by blowing up Grant's base. William establishes later on that it was the Deathstroke gang's original headquarters. But with the base now blown to pieces, it means that the future legacy of the Deathstroke gang will have to be rewritten.
It remains to be seen exactly what the status of the gang is in 2040 following this move. But like every other time travel story, by changing something in the past, it affects the future to some capacity. The longer Mia, William, and Conner stay in 2019, the more the future gets rewritten. While last season established how dark things got in 2040, Star City might now stand a chance at getting a better future.
With Crisis on Infinite Earths coming up, that might also have a huge effect on what 2040 looks like when/if the kids ever return home. Since Mia is now in the present, her visit, along with the upcoming crossover, could also be how they set up Green Arrow and the Canaries. But given that the characters in the present now know a lot about what's in store in their future, the upcoming Arrow episodes may further change the Star City of 2040 sooner rather than later.