Granted, I think World's Finest might just be strange wording (ending it on a batmite arc would be strange) and, who knows, Taylor might continue on Nightwing beyond Heartless.
Action Comics is gonna be Superstars all year-long though, right? Assuming all arcs are three-issues long, there are two writers left this year. Safe to assume one of them it's Waid. The other one who knows, there are many options (King, Taylor, Zdarsky, even Ram V or Snyder).