This sounds unlikely, I think if R* was in serious financial trouble, they would've gone ahead and release GTAIV, not delayed it half a year.
However, stranger things have happened, and like most people said above, R* appears to have been pulling away from Sony this past year. They were an integral part of the PS2's success, so maybe Sony sees it as a wise investment for PS3 and following consoles.
Still, I find it highly unlikely this is true, for most of the previously stated reasons.
Currently Playing: Saints Row 2 | Battlefield 2 | Company of Heroes
Recently Beaten: Gears of War | Super Mario Galaxy | Darwinia | MGS4 | Sam and Max Ep. 4, Portal | Mirror's Edge | Uncharted | Mass Effect
Looking Forward to: Alan Wake | Splinter Cell : Conviction | The Last Guardian | Batman: Arkham Asylum | SMG2 | Mass Effect 2 |