There's still a month to go until we'll get to see the first episodes of DC's Arrow Season 4 or The Flash Season 2, but details about the upcoming seasons have been coming in dribs and drabs over the past weeks, most exciting of all being the official premiere synopsises which have now been released by the CW.
The Flash Season 2
It looks like there's going to be a narrative gap between Season 1 and Season 2 of The Flash, as Barry goes the way of Oliver and alienates himself from the rest of the team. But when a new threat arises he's going to realise that he can't protect the city on his own.
It's a bit odd that there's such a time gap between seasons, I think we expected to witness at least some of Barry's journey into the alternate universes at the end of Season 1 as part of solving the Singularity problem, but perhaps this will be explored alongside the formation of the "Meta Task Force" at the CCPD.
S2E01: The Man Who Saved Central City
"BARRY DECIDES HE NEEDS TO PROTECT THE CITY ON HIS OWN - Picking up months after the Singularity attacked Central City, Barry (Grant Gustin) is still struggling to forgive himself for Eddie’s death. Concerned about putting his friends in danger, Barry has pushed everyone away and has chosen to protect the city on his own. When a meta-human named Atom Smasher (guest star Adam Copeland) attacks the city, Iris (Candice Patton) tells Barry that he needs to let his friends help him protect the citizens of Central City. Meanwhile, Cisco (Carlos Valdes) helps Joe (Jesse L. Martin) with his Meta Task Force."
Arrow Season 4
It's back to Star (formerly Starling) City for Oliver and Felicity as Arrow Season 4 kicks off. When a new threat emerges in the form of Damien Darhk, a danger alluded to but never actually seen in Season 3. Now we have a name for his underlings as part of H.I.V.E. - the 'Ghosts' - who are attacking the city. However it seems like estranged friends Oliver and Diggle are going to remain that way as a result of Oliver's actions towards the end of Season 3.
Finally, and most excitingly, the premiere episode's title points towards something we've known was coming for a while now: Oliver's transformation into the fully fledged Green Arrow.
S4E01: Green Arrow
"MY NAME IS THE GREEN ARROW - Oliver (Stephen Amell) and Felicity’s (Emily Bett Rickards) blissful getaway is cut short when Thea (Willa Holland) and Laurel (Katie Cassidy) pay them a visit and tell Oliver they need his help back in Star City. The city has been attacked by “Ghosts,” assassins led by a dangerous man named Damien Darhk (guest star Neal McDonough). However, when Oliver returns, Diggle (David Ramsey) makes it very clear that he doesn’t want Oliver on the team."
Bonus: The Constantine Crossover
According to Arrow and The Flash Producer Marc Guggenheim, John Constantine (Matt Ryan) will play an exciting role in Arrow Season 4, and will be instrumental in setting up [DC's Legends of Tomorrow](tag:2937021).
“When you see [Constantine] in the show, honestly it feels like we’re doing a Constantine/Arrow crossover, and it’s so exciting… We’re just really glad we got the chance to extend Matt Ryan’s run as Constantine by at least one more hour of television. I think you’ll see he fits very neatly into our universe. It never feels forced, it feels right. Stephen’s on screen vibe with Matt is just very natural, it’s as if these guys had been working together forever. I think people are really going to love the episode."
Constantine's own show only ran for one season before being cancelled, and his return to the universe in Arrow will be linked to the resurrection of Sara Lance/Black Canary (Caity Lotz), as he does have this bad habit of bringing the dead back to life - often with disastrous consequences...