Valve Handheld Plans?

A couple of tweets from Pavel Djundik have details from the SteamDB developer datamined from the latest Steam client. Pavel speculates these are further indications that Valve may be working on a handheld device:
Valve's "Neptune" controller shows up in latest Steam client beta again.

It's named "SteamPal" (NeptuneName) and it has a "SteamPal Games" (GameList_View_NeptuneGames)

This update also added a "quick access menu" and a "power menu"

I have a feeling all these strings related to "Neptune":

Is Valve making a handheld Steam console?