Piracy has always existed, on consoles to, not only on PC, 
By the time GTAIV is released there is a good possibility XBOX360 and PS3 will also be cracked. 
In fact XBOX360 already is , with limitations... ok. 
Hardware is not a issue here , by the time  a eventual PC version will be released, if ever, talking > a year from now, 
the hardware of the middle of the run PC will largely overlap the hardware of the 2 latest consoles, the XBOX360 is already starting to be outdated now. 
Its all a question of , what will be the costs for converting the GTAIV Engine to PC, will the PC sales outweigh the conversion costs ? 
With the PC version there is a big issue of hardware compatibilty , i think this is THE big difference with the consoles versions. 
BTW , I intent to buy a PS3, solely to play GTAIV, so i will certainly buy a PC version. 
PS , just found out about a Keyboard supporting the PS3, hope this keyboard, will make the game a bit more playable