Speaking with IGN at QuakeCon 2018, Bethesda’s Pete Hines said that Fallout 76 not coming to Steam at launch doesn’t mean the publisher will never release a game there again.
“We did not announce ‘all future Bethesda games will not be on Steam,’” Hines explained. “That is not what we said. We said ‘this game will be available exclusively on Bethesda.net.’”
When asked whether Doom Eternal would be skipping Steam as well, Hines said they don’t know yet. “We haven’t decided on anything else, this is specific to Fallout 76 given the kind of game it is — it’s an online, ongoing game,” he continued. “
Source: IGN.com Fallout 76 Avoiding Steam Doesn't Mean All Future Games Will Too, Bethesda Says