PPG covered this rumored title recently and have just received confirmation from Konami that it is indeed coming in 2010 for Xbox Live Arcade, PSN and PC through Steam.
Story info is pulled straight from the press release:
In Rocket Knight, players take on the role of a fiery opossum named Sparkster who returns home to the Kingdom of Zephyrus after 15 years to find it in shambles. Using wits and a trusty rocket pack, players must steer clear and overcome a hostile wolf army looming to take the lives of the Zephyrus people.
Gameplay is 2.5D (remember the early days of 32-Bit gaming with games like Clockwork Knight 1 and 2 for Saturn or Pandemonium for PSOne, PC and Saturn?). The classic gameplay of using the rocket pack to bounce off of walls to gain higher jumps will be returning (have there been many games recently to feature this gameplay mechanism?) along with many other gameplay options that have simply been gone from gaming (since games are either trying to be GTA clones or Halo clones, it is not a surprise).
Rocket Knight by Konami- website
Rated: E for Everyone
Due: 2010 (digital download only)