According to Assignment X's interview with Marc Guggenheim, it's implied that Green Lantern may be coming to the world of Arrow and the Flash some time soon.
Here is the implication:
AX: Is the question also, “Where do we do it?” or is it like, “No superpowers, it’s on ARROW, with superpowers, it’s on FLASH”?
GUGGENHEIM: I think we started the season off with that dogmatic sort of division and I think we’ve all – Greg, Andrew and I – collectively softened on that. We always had a plan for this year in terms of the Atom, in terms of the world of Ra’s al Ghul. And again, it’s just feeling what feels right. I’m sure there’s a way to do GREEN LANTERN in the world that we’ve created on ARROW and FLASH. How and when and why that happens, part of it’s a creative thing and part of it’s what is D.C.’s plan and certain decisions get made way above our heads. We’re very happy with the characters we’ve got right now.
But you can read the entire interview here: http://www.assignmentx.com/2015/marc-guggenheim-arrowthe-flash-part-2-interview/