So nothing but speculation still as no one will know till it's announcement.Kotaku reported that Fallout 76 will be “an online game of some sort.” Polygon has also heard the game will feature multiplayer.
Based on the developer it wont be online as that's a different studio ZeniMax Online Studios. Then again this could be the announced studio from a few months back.A press release sent out by Bethesda said Fallout 76 is in development at Bethesda Game Studios on PlayStation 4, Windows PC and Xbox One
Link - https://gamingbolt.com/bethesda-opens-new-studio-in-austin-texas
Bethesda Game Studios, best known for Fallout and The Elder Scrolls, have opened up a brand new studio in Austin, Texas; well, “opened up” is a bit misleading, since what has actually happened is that they have absorbed BattleCry studios; BattleCry Studios was founded in 2012, and is led by Studio Director Doug Mellencamp, who is a industry veteran and has worked on several AAA games. His experience should prove to be useful to Bethesda.