Has one of the GTA 6 protagonists been already presented in GTA4?

Do you recognise this gentleman from GTA IV? It's Jerry Kapowitz - the homeless, who found famous diamonds in the garbage. But what does he have to do with GTA VI? And what does Niko Bellic have to do with it?

Actually, the link can be quite significant. Of course, these are only speculations, but listen to the recording from the Weasel News. The one that interests us starts at 1:13:00.

So our dear Jerry has got the diamonds worth 2.000.000 $ and is planning to open a shop with weapons and an off-licence…in Vice City! We should add that Jerry's a veteran from Vietnam, who's now famous thanks to the mentioned audition. If you remember the adventures of Niko and the team, then you know that many people were after those diamonds. Now, when the stones have got found and monetized, what's more - everyone even know where to look for their new owner - do you reckon, they'll not want to get them back?
I don't say that Jerry will be on of the main protagonists, but in the upcoming version of Grand Theft Auto he could be an episodic character, whom, e.g., we'll have to rescue on one of the missions.

Letting the fantasy go even further, imagine Niko's comeback. Obviously we know that the actor dubbing the GTA and R* protagonists, both are against each other, and wouldn't it be an ideal occasion for another Josh Feinman’s flick in the nose?
Niko wouldn't have to say anything. Let's imagine the scene where Niko’s been forced to taking back the diamons/ money. So he flies to Vice City, with the sniper he's keeping an eye on Jerry, who earlier got a tip off from one of his people, so we (now as the GTA VI protagonist) blow Niko up. R* showed in GTA V that he has no difficulty in saying goodbye to his heros (Johnny Klebitz) and numerously proved that anyone who'll get on his nerves may count on a sneering fate in GTA.