Ars Technica confirms after data miner speculation
Twitter SteamDB (an account focused on 'tracking all things Valve and Steam') dug into recent a Steam beta update (code-named 'Neptune') and found references to a device dubbed "SteamPal". A few hours later, Ars Technica say they can confirm an existence of a 'Switch-like portable gaming PC' in development at Valve.
Currently not much more details are known, however at least one SteamPal prototype has been spotted which appeared to be Switch-like, however much wider. It is speculated this extra size will allow Valve to pack in an array of gamepad buttons and triggers, joysticks and at least one thumb sized touchpad.
Valve co-founder Gabe Newell was recently asked earlier this month what the company's plans were for the future of console videos games, in which he gave an indirection answer stating "you will get a better idea of that by the end of this year... and it won't be the answer you expect. You'll say, 'Ah-ha! Now I get what he was talking about" - so it seems like an official announcement is more than likely on the way.