Well, that was interesting.
The fact that this forum environment allows Mikael to come along and give his opinion right back to the fans is one of the amazing benefits of this medium, I must say.
I think the major issue this conversation has had all the way along is a definition of what "selling out" means. Myself, I would define it as (in this case) the act of a musical outfit, who consider themselves artists, knowingly and intentionally altering the music they record for the specific purpose of financial gain.
Firstly, seeing as the only person who knows the intent of the artist is the artist, the call of selling out by a fan is an assumption. Secondly, artistic value is relative, and is not subject to finances (although there often seems to be a correlation) - I think this has been MMCPA's biggest point.
Thus, so long as the members of Opeth are motivated by means other than to be financially benefited in the creation of their art, then the term "sell out" is a misnomer. However, if you think the new music they produce sucks, then you are entitled to say it sucks. But don't call it selling out because you don't like it.