After a flying start two years ago when it was the key piece at NBC's upfront presentation, Revolution has just been cancelled. The JJ Abrams/Eric Kripke post-apocalyptic drama is long ways from where it was last season when it was riding high with a lot of buzz and solid ratings behind The Voice on Mondays. The heavily serialized series started to lose steam after the long hiatus between the fall and spring half-season. And it has been a ho-hum performer in the low-trafficked Wednesday 8 PM slot this season, a shadow of its former glory. It has been stable, keeping the lights on in the hour. That wasn't enough, especially given the high price tag on the show. Hope for Revolution getting a 13-episode final chapter took a further hit yesterday when NBC picked up two new series from series' producer Warner Bros. TV, including comic book drama Constantine, which had been considered a potential replacement for Revolution. Keeping Revolution was important to studio WBTV, while NBC was open to letting go and it just did.