Grand Theft Auto 5 for PC may actually be a thing, according to this Amazon.fr listing.
PC ports of Rockstar's games have always been iffy. Though the past few Grand Theft Auto titles, L.A. Noire, and Max Payne 3 have all made it onto the PC, only the last managed to make it onto the PC platform in a timely manner. Even then, Max Payne 3's port to PC was due to the legacy of its predecessors.
Back in October 2012, Rockstar announced that Grand Theft Auto V would be touching down in Spring 2013. Unfortunately, though the title was confirmed for Xbox 360 and PS3, Rockstar neglected to mention anything about a PC release. Concerned fans put together a petition on Change.org for a PC release, which has garnered over 146,000 signatures so far.
There may be hope yet. Recently, Grand Theft Auto V for PC was spotted on Amazon.fr. Though Amazon listings aren't the most reliable source, the listing has remained there for quite a few days and has yet to be removed. Though it doesn't serve as any official confirmation, it certainly is a good sign.