what do you guys think. it has currently sold over 30 million, and with expected next gen versions/PC can the game make it to over 40 million? I think it can if it releases on nextgen consoles in 2014. 

it can reach 40 million, it would be hard for it to do so but it can. (if it launches on PS4 and XB1)

maybe yes, maybe not

It will easily surpass Mario Kart Wii

If it releases on next gen consoles then I could see it happening.

Well if its spread out over that many consoles, probably no more than 45 million.

I find it interesting that Super Mario Bro's (NES), Super Mario World (SNES) and Wii Sports (Wii) were key to their systems overall success and the other systems sold by Nintendo lacked that aspect. N64 (nothing), Gamecube (Not sure), Wii U (Nintendoland)

They're 50/50 with this approach. They might want to change it in the future to always having a system selling title packed in. Since that is what works for them. When they mess up the pack in title they (Nintendo) suffer for the whole generation I have noticed ^^

GTA5 has an amazing following.  I wonder what they're waiting for when it comes to releasing on PC...if I was rockstar I would even port it over on PS4/XB1. That game is huge and could keep pulling numbers over time like a SMB.

Why do people praise super Mario bros for its 40m sales when over 28m of them were down to the game being bundled with the console in the US?
I suppose by that logic, the ps1 demo disk is the highest selling game of all time.

Considering GTA SA is still selling quite well 40 million plus is possible.

Because it still sold greatly and was the main reason people bought the NES. And let's be honest here, that game changed the face of gaming forever.