I think they were genuinely surprised how well GTA Online has done – both from a revenue perspective via shark cards, and also from a player engagement angle. There were apparently single player DLCs that were scrapped because they put all their focus and resources against Online. It is a shame – given that some of the DLC for GTA IV were fantastic (The Ballad of Gay Tony), but I can understand their reasoning as it's hard to argue with how successful GTA Online has been.
I will also say that I cannot remember the last time I played GTA V, as opposed to GTA Online. After I completed the main story, I don't think I went back. In previous games I would have, because there would have been so much to do in the sandbox that they created. But I just do that in GTA Online instead. I still play GTA Online quite alot – whether it's doing solo heists, or jumping into different races/challenges/missions with randoms.
But I agree that they are in danger of parodying themselves. I am really curious to see how GTA Online evolves when GTA VI launches. Will it be an add-on/extension of the existing GTA Online world? That would make sense as it is the same time period (so the vehicles will be of a similar ilk). But then they will have players starting the game with millions in their banks – which would likely impact shark card sales (or maybe not if they are still raking in millions from them for a 10 year old game!). If it is going to be a standalone world, with no character carry-over, then I feel it needs to be quite different in structure, as I think many people would not be too willing to start the grind from level 1 again – especially if it involves buying vehicles that they have already bought and used in GTA V!
But am still really excited for GTA V and can't wait to hear more about it and see the next trailer whenever it drops.