I really, really hope that EGM is right and LittleBigPlanet will see a PSP port. To say that we loved LittleBigPlanet is such a gross understatement I can't think of an appropriate analogy so the proposition of not having to stop playing when leaving the house is an exciting one to say the least.
Admittedly there's no actual evidence to back up these claims, as reported by Kotaku, nor any information about the game other than the claim it does (or at least will) exist. This isn't the first time such a rumour has sprung up, though, and it definitely makes sense - LittleBigPlanet has become something of a flagship title for Sony's PS3.
Supposedly cross-platform action between the PSP and PS3 versions of the game would be possible. However Media Molecule, LittleBigPlanet PS3's developers, are apparently not involved with the PS3 port instead working on other projects - a potentially equally exciting snippet of information.
Come on Sack Boy, get a move on and come to the PSP.