It looks like the Steam Deck could just be the start of Valve's plans to move into the handheld gaming space, according to the designer of the device, Greg Coomer, who claims the company will "continue making devices in this product line." in an interview with PC Gamer.
The statement from Coomer lines up with previous statements from Gabe Newell, who has previously stated his desire to establish "a product category that ourselves and other PC manufacturers are going to be able to participate in." One device does not a category make, so it'll be interesting to see what other devices Valve are working on.
Speaking to PC Gamer, Coomer talks about how the company hopes to establish an "actual category" where there are multiple different device choices within it. Much like Microsoft's approach with Surface, though, the company hopes to inspire other PC makers to fill the space too. "If we're right about that, then there will be more choices within the category, where other manufacturers are participating, making handheld PC gaming units themselves, and calling them something else."
The Steam Deck then is intended to be a kickstart mobile gaming based on Steam's platform. SteamOS has been around for a while, being used on Steam Machine, but it's finally reaching a level of maturity that is making it a serious competitor to Nintendo's Switch or gaming on Windows. Coomer talks about the different ways to approach the market, with devices potentially focusing more on battery life and less on raw power, as being one example.