I think people are interested in consoles because they want access to those communities. There's a lot of people that wont deal with PC gaming, and those people wont use a Steam Deck either. I would want my game to be available to console gamers, for profit and to share my with with as many as possible. As good as the Steam Deck may be, I don't think it will lessen interest in the video game consoles.
You can't just become a console developer though... You need to have proven releases on desktop or mobile before any console maker will even let you touch their devkit...