It must have a decent enough uptake amongst Bethesda fans. Over 200 people across my 5 Elder Scrolls Online guilds are playing it. Also the server drop off at the moment is extremely noticeable. However if that is the majority of Fallouts player base, they are going to ultimately lose money, because ESO must be a much bigger cash cow overall.
Also it looks like the servers for both games are tied, because there have been huge server issues since Fallouts launch. That must be annoying both fanbases.







