Good Question.
Right now and in the past MSM stands for "Main Stream Media".
In the future we will be able to retain that acronym but the meaning will evolve to either "Minor Stream Media" or "Minimal Stream Media". "Micro Stupid Media" and "Mainly Stupid Media" are also candidates.
Stay tuned and enjoy watching the Internet complete the near total destruction of the "MSM". It's will be such fun.
Alt Media?