Dylan O'Brien is contracted for season 5B, 6A and 6B. Jeff Davis said that on the Teen Wolf news. Dylan O'Brien will also be filming The Maze Runner which might be a scheduling conflict. But Teen Wolf might take a little break this time, or film sooner than expected. No real dates are confirmed neither for Teen Wolf or The Maze Runner.
In Season 5B we'll see everything we have never seen on the TV Show. This will be about Scott fighting for everybody and making things right. We'll see The Beast. But who will defeat it?
Colton (27) is back on Arrow season 4. He's confirmed for Episode 12 and rumored for Episode 13. Episode 13 might be about a move to Central City.
So is Roy Harper moving to Central City? And helping The Flash? Nothing is confirmed. But with Harrison Wells from Earth 2, Cisco, Joe, Caitlin, Iris, Patty and more they don't really have a second superhero. In Arrow they have, Green Arrow, Black Canary, Speedy, Spartan/Black Driver Diggle, Felicity and more. So they really get the help. With the speed of Barry and the skills of Roy and the help of Cisco and Caitlin and the push of Harrison Wels and Iris and Joe's advice Team Flash would be perfect.