Most GTA Vice City characters would be unlikely to return in GTA 6 if the latter game took place in the modern era.
The two main reasons to consider are:
- They would be far too old.
- Most 3D Universe characters aren't relevant in the HD Universe.
The former reason is self-explanatory. GTA Vice City canonly takes place in 1984, whereas any modern game would take place around 2022. That's a difference of 38 years, which is a great deal of time to add to the adult cast. For instance, if Tommy Vercetti were born in 1951, he would be 71 years old now.
Needless to say, it wouldn't be as exciting to see these beloved characters act as geriatric criminals in GTA 6.
The few reasons why most GTA Vice City characters won't return in GTA 6
Many Grand Theft Auto fans assume that GTA 6's primary setting is Vice City. The idea of "Grand Theft Auto VI" taking place in Vice City sounds perfect, not to mention that fans haven't seen the region in well over a decade. Naturally, that has led to discussions on whether some old fan-favorite characters could return.
Unfortunately, they are unlikely to return for a number of reasons. If GTA 6 takes place in Vice City, then there's a strong chance some characters can be referenced. However, being referenced and actually showing up isn't the same thing.
There is also the possibility that GTA 6 won't take place in Vice City, limiting a GTA Vice City character's potential to show up.
These characters would be too old in the modern era
GTA Vice City would've canonly happened nearly 38 years ago if GTA 6 was set in the modern day. Given the dangerous life of crime and how so many characters die in a single game, it would be unexpected for some characters to survive nearly four decades later.
Even if they did survive, the Grand Theft Auto series doesn't feature old characters in an active light (for obvious reasons). Many of the characters would be in their 60s to 70s if they were still alive.
If some characters did return, they would be like Willy from Love Fist. He returned in GTA 5 (back in 2013) in a very minor role where Trevor had to take his gold tooth. He's noticeably older in this role and doesn't put up much of a fight.
3D Universe vs HD Universe
Even if GTA 6 occurred in the 80s, there is still the issue of separate "universes." Characters from GTA Vice City are part of the 3D Universe, whereas characters from modern games are from the HD Universe. GTA 6 would be a part of the latter universe.
Essentially, the two different "universes" are separate entities. 3D Universe characters (like from GTA Vice City) might be referenced or used in small cameos in the HD Universe games. However, the HD Universe series of games focuses mostly on using characters from the most recent titles.
There are some differences in the lore (such as how different Los Santos looks between games).