Have you seen the videos / read about the game? It is already quite certain that it will not be a WoW/GW2 hybrid.
BGS and ZOS do communicate, and BGS do help ZOS with development, but BGS are not spending a lot of time on it. They are focused on their own games. ZOS have access to all the lore from TES without anyone from BGS having to tell them anything, as it is all written down.
Having people who are used to developing singleplayer games making a MMO doesn't really make it worth any more than if people who are used to developing multiplayer games are working on it.
ESO is not developed by Bethesda Game Studios, who will continue working on their singleplayer games (Fallout and TES), so don't worry.
Elder Scrolls Online: ZeniMax Online Studios
Elder Scrolls Series: Bethesda Game Studios
World of Warcraft: Blizzard Entertainment
Warcraft Series: Blizzard Entertainment
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