Rockstar doesn't re-use protagonists. Seeing as the ending varies from player to player, I doubt Rockstar will include the main characters in the next GTA installment.
Rockstar has also never focused so much on the story. It went to far far greater lengths to develop these characters with far more unique missions, a far better planned plot and story, a far tighter story arc, much more focus on character development related to plot, etc. GTA stories and characters are usually just jokes used as excuses to move you around the map. The stories are always terrible, nonsensical with plot arcs that are all seemingly unconnected and appear out of nowhere based on silly stereotypes and jokes, with the same 2-3 mission types. Missions and story and character development in GTA is usually horrible. GTA V spent exponentially more resources on the story arc, development, and mission quality and pacing than all other GTA games combined.
So past history of GTA characters and story probably isn't a good indicator because if you had used it to predict GTA V, you'd have been very wrong, so using it to predict VI could also be very wrong.
I would have been very surprised to see GTAV about Nike or CJ.
However, I would not be surprised to see VI about Trevor or Michael, or a young Brad, Trevor, and Michael, or Franklin and Lamar, or any other returning cast. I wouldn't bet on it! But I wouldn't be surprised either. Especially young Trevor and Michael.
You're wrong. Yes, a lot of the plot arcs were silly and a lot of characters based on stereotypes but the characters have always had their place and story. Rockstar is not in the habit of re-using protagonists in the GTA games. Each character (In GTA V's case, 3 characters) has their game. One game for them. That's how it has been. That's how it will always be.
GTA VI will have a different protagonist(s) and while some characters from GTA V may make an appearance, that's where the line is drawn. There may be mention of Michael, Trevor and Franklin but I doubt they will get their own game again.
Although I would certainly love a DLC expansion to GTA V detailing some of the events in the lives of Michael, Trevor and Franklin before we met them in GTA V. Sort of like what Episodes From Liberty City did, expanding on the backstory of GTA IV.
come now, we both know that if you measure the number of missions related to the main plot, the number of characters genuine relevant to the core plot, the number of unique mission gameplay, and numerous other objective factors such as voice acting hours, time between missions based on travel, number of missions versus side missions or gameplay versus side gameplay related to the main plot, that GTA V has a far far more story-focused and plot-focused production
it's not even comparable... GTA SA or IV's story focus, cumalatively between all 3, is probably less than just 1 GTA V character lol it's by that large of a margin
Rockstar even says this and the the critical metacritic aggregate agrees with it, search any 10 random top reviews and they all explain and support this. or google interviews such as this one http://www.theguardi...to-5-dan-houser where Houser specifically says the narrative and mission design 'goal' was different for GTA IV than SA and VC, and they wanted to do things even more "different" in their narrative approach with GTA V
Houser even said they hoped that GTA V, unlike past GTA games, would really change how 'all games told stories' http://www.polygon.c...ancy-and-future and his brother, he never gives interviews and was known to have massively 'burned out' after GTA IV, suggested to http://playboysfw.kinja.com/criminal-mind-the-reclusive-genius-behind-the-grand-th-1479684025 pretty clearly that he wanted more narrative relevance with GTA V and to really take the series to a new level of storytelling
they even hired new narrative team members such as cutscene director because they want to take the story narrative focus on GTA much higher in V than past games. past GTA games basically just had a few people doing sound capture for voice work, for GTA V they did full mo-cap/voice-cap at the same time with a full team of professionals that resulted in far far more story assets than all other GTA games combined. whether this was aided by new technologies doesn't change that once again that it resulted in a vastly different production and narrative approach for GTA V than other other GTA
the script of GTA V was over 1000 pages.... GTA I-IV combined were barely 340
please don't misunderstand objective and subjective elements. this isn't whether or not you like Tommy or CJ or Vercetti better, like metropolitan cities skyscrapers to deserts or forests... it's about an objective measurement in provable qualitative or quantitative ways that show, without a doubt, that the GTA V production of its story and plot, and the missions, took a significantly and notably different approach than past games
i mean, you could have said GTA I-IV has never had such a strong focus on a single plot arc and always has random new irrelevant joke characters with long story orcs as part of the core story, so of course so will V, and you'd be wrong
you could also say GTA I-IV never had multiple protagonists, and you'd be wrong
so you could just as easily be wrong about a returning protagonist.