Fishing has appeared in San Andreas (briefly) and RDR2 (seriously). Whether GTA 6 has it is an open question - we work through the history first.
Fishing in past Rockstar games
GTA San Andreas had a small fishing minigame in some side content. RDR2 had a serious fishing mechanic with rod variety, lure choice, fight mechanics. GTA V had no fishing.
Whether GTA 6 returns to fishing is a design choice, not a technical one.
Why the Florida setting suggests it
Real Florida is a fishing economy. Charter boats, pier fishing, deep-sea charter. The visual vocabulary of Vice City marinas already includes fishing. The bar is low for Rockstar to include fishing as atmosphere; medium for it to be a real system.
We don't commit. We do say it's plausible.