It's typical Rockstar marketing.
1. Announce a game to be released on consoles, make no mention of a PC release but don't deny it either.
2. Release game on consoles.
3. Announce a PC version a few months after the console release.
4. Release on PC.
This way, they sell the game twice to a quite a few people, making double the money they would have made if they released the PC version at the same time as the console version. They've been doing this successfully with every major title release since GTA 3 in 2001.
The only exception to this is the Read Dead series.
The first Read Dead game wasn't really developed by Rockstar, it was developed by a company that went bankrupt near the end of release, Rockstar bought all IP from them, then released the game on PS2 and Xbox. Since they didn't actually develop the game, they weren't going to port it over to PC.
The rumours for the second Read Dead game, is that at the end of development for the PS3 and 360, someone messed up the source code to a point where it would have been quicker, easier and cheaper to just remake the entire game for PC. But of course, that wouldn't have been financially viable and since they didn't announce a PC release, it didn't really matter too much to them. Of course, this is a rumour and the only proof to it is people who have basically said "I know a guy who knows a guy who knows a guy who works at Rockstar and they said this is why it wasn't released on PC."