Probably. The fact that GTA 5 has made enough money to fill several Olympic sized swimming pools, it is no doubt that Rockstar will be working on or planning the next game in the series. There were already people waiting for GTA 6 to be teased after the release of GTA 5. Speculation like in this article shows that.
Although, the disappointment that was GTA online (heists spring to mind) some people will be wary about trusting them about online play again. Yes, online was fun, when it worked close to the launch of online. I understand that a game with a feature this hyped would encounter problems, but it did silence the experience slightly.
All of that said, the single player was revolutionary. If there was a GTA 6, people would expect more out of the single player. But how do you improve upon fantastic? People are still playing games like the original GTA, Vice City and more up to date GTA 4. It shows that some traditions, will stay with us.
