Didn't you hear? They announced that "they have no plans for PC or Wii U" and will only consider it "if there is a market for it"
http://www.pcgamer.com/2012/11/19/gta-5-pc-version-merely-up-for-consideration-says-rockstars-dan-houser/
And yes, the GTA 4 port was terrible but L.A. Noire didn't have that problem (that I remember). It was a decent port, the faces looked weird but that's not a porting problem, the face tech simply doesn't work well on monitors and... well I don't want to start a discussion about it. Let's keep things on topic
Also, Max Payne 3 had it's PC version on Day-1 and I understand it was all propperly done (didn't play it myself). And like the petition says, GTA 4 ended up having a great mod community so good or bad port, it was still loved
It's not about asking for a rush job, it's the old dance where Rockstar says "No PC version" and PC gamers scream untill they announce the PC version we all knew was going to happen 6 months after. It's mostly damage control to make sure that happens, instead of getting another Red Dead Redemption