Joystiq mentioned a rumor about a PlayStation 2 port of Ratchet & Clank: Size Matters and it looks like it exists. Besides listing the game, Gamestop updated the page with some official looking PS2 box art too. Even the ESRB updated their database with Ratchet & Clank: Size Matters listed as a PlayStation 2 game.
Sony has yet to confirm the port, but chances are good we will see it sometime in 2008 at a slightly reduced price. Until Sony officially announces it plenty of questions remain about what content will be in the PlayStation 2 version. I doubt anything will be censored like the Syphon Filter: Dark Mirror PS2 port, but tweaking online play to work on the PS2 seems up in the air.