A Norwegian retailer's pre-order page had said that GTA V for PC would release on the 18 March. While there is no guarantee that this information could be accurate, such leaks from retailers usually turn out to be true.
via N4G: pc news feed http://n4g.com/news/1416446/gta-v-pc-version-likely-to-release-by-march
via N4G: pc news feed http://n4g.com/news/1416446/gta-v-pc-version-likely-to-release-by-march