It has been announced via OneofSwords Twitter account and blog post that Call of Duty Modern Warfare 3 will have dedicated servers on the PC version.
This was also confirmed by Noah Heller at Gamescom, when speaking with Eurogamer he stated that:
The big announcement today is that we’re supporting dedicated servers for PC, which is really cool.
This comes after dedicated servers were ditched Modern Warfare 2.
The game is out in November and you can preorder from ShopTo on PS3, Xbox 360, Wii and PC