http://kotaku.com/5033671/rockstar-c...-gta-iv-for-pc
The rumors have been circulating for months, but today Rockstar officially confirmed that Grand Theft Auto IV will be hitting the PC on Nov. 18 in North America and Nov. 21 in Europe. "We are very excited to be releasing the PC version of Grand Theft Auto IV," said Sam Houser, Founder of Rockstar Games. "The whole team is dedicated to bringing an amazing gaming experience to the PC. The game looks and plays beautifully on PC and we can't wait for people to play it."
It looks like the PC version will be ported by Rockstar North, though I've pinged Rockstar to be sure. I've also asked them about pricing, DLC and system requirements for the PC version.