Not officially confirmed

• Map size in square miles or km
• Online multiplayer plans — no GTA Online VI announcement yet
• Microtransaction model
• Single-player DLC
• Cross-play or cross-progression between PS5 and Xbox
• Modding support
• Specific mission count or main story length
• Full cast list and voice actors
• PC release window

Be skeptical of

• "Leaked map" images — most are fan reconstructions from trailer frames
• Specific weapon lists, vehicle counts, business types
• Mission walkthroughs (the game isn't out)
• Anyone selling "early access" or "beta keys" — those don't exist

Where to get real updates

• Rockstar Newswire — rockstargames.com/newswire
• @RockstarGames on social
• Take-Two earnings calls — sometimes mention business model details

Everything else is rumor until Rockstar posts it.