I think that I would start thinking that Opeth was "selling out" if I saw an album with very short tracks on it. While many of the musical aspects of Opeth now and through it's entire life as a band have not necessarily been unacceptable to the general populace-- in fact, I have shown some lighter Opeth (Face of Melinda for example) to people I consider "pop-heads" (it's like a metalhead, but broken) and they loved it. That said, the death metal growling part of Opeth (my favorite part) is something that would have to go for it to become really popular, but it's never been the sole style of vocals present, even on their heavier albums. Really, the only thing about Opeth that has NEVER changed and probably will ONLY change if an album specifically designed to make money is released is the fact that the vast majority of their songs are not designed to be played on the radio. While they don't follow a standard structure musically or lyrically (name one Opeth song with a repeated chorus. Okay, there's probably one or two but the point is it's not common) the main unavoidable, ever present difference between Opeth (music) and "pop" (noise) is the song length...
...and the quality, but I won't get into bashing Carrie Underwood just 'cause she sucks.
Listen to Psyclon Nine. I guess it's technically called "aggrotech" or some form of industrial, but it's basically electronic black metal. Sort of.
