Earlier today, Alan Wake was found on Steam's registry. This could be all that is needed to confirm the existence of the PC release, after Sonic Generations was also placed on the registry, where the PC version was later confirmed and released.
Just after the reveal of Alan Wake's American Nightmare, Remedy’s Aki Järvilehto said in an interview:
“We have received feedback from a lot of PC gamers, and I have to admit that yes, we somehow ignored that. Let’s see if in the near future we could have some positive news to tell you about dating!“
Go here: http://www.nave360.com/alan-wake-found-on-steams-registry/ for full details and pictures.