There may be some players that aren't aware that Steam had a feature which was embedded into the PC client, and has existed for more than nine years. Back in 2012, Valve unveiled its Big Picture mode, which aimed to bring PC gaming to any HDTV. Unfortunately, it seems to have gone most of its life being relatively unused, so it's probably not surprising that the company has now said it will be replacing it in time with the interface that comes with the Steam Deck.
In a post on the Steam Big Picture community page, an employee, who goes by the handle _autinp_valve, did confirm that the company will be dropping this mode for its PC client and swapping it out for the UI that's built into the Steam Deck instead. The response came after another user asked a question in the forum about whether or not the OS for Steam Deck would be converting to Big Picture. As it stands, there is no official date yet for when the conversion will be happening.
It's also not known whether putting the Deck's UI onto the Steam PC client will prove to be a popular move, but the commenters in the community seem pleased with the announcement. It's entirely possible that Valve simply just wants to phase Big Picture out and make a more universal user experience for when the Steam Deck does arrive. Big Picture mode has not really been that popular, much like the now-discontinued Steam Controller, but this change could be the right move.
With news coming out all the time, the device is shaping up to be a decent-sounding piece of hardware, especially for those who are interested in PC gaming on the move. With recent announcements that the Steam Deck will fully support mods, it's already looking like it may stick out against other competing hand-held consoles, such as the Nintendo Switch.
Of course, that's not to say it hasn't come across its fair share of problems. While on the surface, it appears to be an ideal portable piece of hardware for gaming, there are some downsides which may or may not be fixed by Valve before release day. For example, although it's capable of playing games from a user's Steam library, some online games such as Dead by Daylight may not work properly. This is due to something that's not related to the games per se, but is something Valve is looking to fix before December.
The Steam Deck will launch in December 2021.
Source: Steam Community