Way back in the day, Valve made a game controller that was a little bit out there. Rather than having two analog thumbsticks and a traditional D-pad, the Steam Controller had two touchpads that the player ran their thumbs across. It was certainly innovative, but it never really sat well with potential users.
A few months after the Steam Controller's launch, Valve provided yet another directional input in the form of an internal gyroscope--a feature that Valve never mentioned in the Controller's advertising. It was surprising, but again, wasn't quite enough to get people to throw away their Xbox controllers in favor of the Steam Controller.
On the Steam Deck, Valve has learned its lesson. The Deck has plenty of thumbsticks to use if you prefer them over the touchpads that the Deck also provides. And this time, motion controls are an advertised feature for the Deck.
In an interview with Rock Paper Shotgun, Valve designer Greg Coomer promises there "isn't something secret embedded in the Steam Deck that we're going to turn on later." What you see is what you get.
That said, the Steam Deck will still get regular updates after its arrival next year, they just will be mostly focused on the Deck's software. Coomer says that Valve likes to include some "inherent futureproofing" in its hardware, and the Deck is no different. He specifically mentioned the Deck's ability to stream games from another PC, allowing the Deck to play games of the future that might exceed its internal specifications.
Additionally, Coomer promised to keep "iterating on" the Deck after launch to make sure the suspend and resume features are "as seamless as possible."
The Steam Deck already has some big names supporting it. Xbox head Phil Spencer said that playing Halo "feels good" on the Steam Deck, while Epic's Tim Sweeney called the Deck "an amazing move" by Valve.