Twilight Eclipse hasn't been released yet, and it still hasn't been confirmed if Breaking Dawn will be split into two movies or not. But Twilight fans are already thinking about the strange period that will follow Breaking Dawn... Will it be the last movie in the Twilight Saga? Well normally yes, but knowing the studios, I guess Summit Entertainment would be more than happy to produce a Twilight 5 movie. And I bet they've been at least considering Midnight Sun, the last Twilight novel written by Stephenie Meyer. Twilight Midnight Sun is supposed to be the retelling of twilight from Edward's point of view instead of Bella's.
Unfortunately this novel hasn't been published, because Stephenie Meyer didn't appreciate to see her early work on the novel leak online. Back in 2008 she said:
Although irked by the leak, Stephenie Meyer is now sharing a partial draft of Midnight Sun online:
I'm pretty sure that she's been working on it since then, and my bold guess is that the novel Twilight Midnight Sun will get published not long after the release of Breaking Dawn the movie... And then Stephenie Meyer and Summit entertainment may agree to produce Twilight Midnight Sun the movie (and there is no doubt in my mind that the actors of the main cast, Robert Pattinson, Kristen Stewart and Taylor Lautner, would be glad to keep the franchise going for one more film).
Still if they don't make a live-action movie, there is still hope that they produce an animated movie: Twilight the Graphic Novel was published not long ago and looks already ripe to be adapted as an animated movie. And this could be a way to satisfy the fans if for whatever reason a live-action film wouldn't be possible...
But nothing is set in stone yet of course, so all this is just pure speculation. So let's pray for Stephenie Meyer to publish the Twilight Midnight novel and for a movie based on that novel to be greenlit!