yes it is in November, just googled it.
"As previously rumoured, Rockstar have now confirmed that GTA4 is coming to PC and is a Games for Windows Live title. So with higher resolution, higher framerate, 360 control pad compatibility and extra exclusive online play - GTAIV on PC is looking to be the best version to own. The GTAIV PC release date in Europe is the 21st November and in the November 18th in North America."