Good article, even thought it's more "Glass Half-Full" than "Glass Half-Empty."
I see the situation as more Half-empty, sadly.
First let's just look at pure numbers. SteamOS is targeting games, first and foremost; so is the consumer. Therefore the number of games available to the platform is incredibly important.
Doing a rudimentary search at the following two pages (which is already imperfect due to counting downloadable-content for games toward the whole number, but the point still stands.)
587 titles for Linux vs. 8744 for Windows at the time of this comment.
This number will undoubtedly increase over time, the more important question is When? or How long will it take?
Going by the length of the last generation of consoles, I can easily see it taking another console generation or more (8+ years) for Valve to play the catch-up game. Another consideration is what percentage of Linux games compared to Windows would be considered acceptable (ideally 50% or more would be ideal.)
Also Valve has stated in the past that entertainment apps are put on the backburner at the moment (Netflix, etc.) so that's another question dependant on an answer of time.
I can't even imagine to speculate Valve's prospects on mobile at this time given their current situation with just SteamOS and games.
At the end of the day I can see Valve successful with their endeavors, it all just comes down to a question of When?