Sorry, but that's nonsense, and it is quite obvious you know very little about subject.
Have you wondered how Valve with Steam platform deals with it? Simple. They have one supported platform - most popular Linux desktop OS - Ubuntu. For every other platform people package it as required, and have short instructions how to setup. As distributions for 10 years now follow Linux Standard Base (or LSB), it is very easy to tune software setup without need or intervention from developer.
Also good software just use proper library calls, which are dynamically found and linked as required. Library versions are stable for very long time, kernel version is very stable for long time. As long this is true, support costs are minimal and major costs are porting itself.
I've worked in the IT business for many years, and no, it's not nonsense.
What Valve does is making a machine that supports WINE or something similar.
BUT! The Steam console will NOT be able to support the more complicated games. So forget about getting it if it's only for not letting Microsoft get a bit of your money.
http://www.tomsguide.com/us/steamos-faq-machines,news-17614.html
So no, you are completely wrong. The Steam box will not be a "way out" for Linux enthusiasts.
Also, it will NOT make developers race out and port for it. Most of the bigger companies don't even support the Steam philosophy.
AND what you write about library/kernel support .. I have to laugh. Windows has a much longer life span in terms of support than fx Ubuntu.
Also, Linux is constantly developed, patched, and modified by people who could theoretically build into it any sort of security hole they wanted, and you'd never know. This is the difference between a commercial, guaranteed product and public development.
If you feel Microsoft are scum, I can't imagine what you think of Apple (well probably the same as I do) ...