Unless the Opeth bus slid off a cliff, I highly doubt that Opeth is dead. From my vantage point, Mikael coming out in public and disbanding Opeth will be the only true death.
Since I "found" Opeth in 2001, they are by far my favorite band. I have been listening to "metal" since I was 10 when Led Zeppelin hit the scene. Here I am 37 years later, having lived and listened through the entire career of metal "gods" such as Slayer, Metallica, and so many others. For me, Opeth's music is beyond comparison. It's almost impossible to describe Opeth's music and it's importance in my life. Sure, if I had never heard of Opeth I'd have another favorite band. But the quality over the span of years Opeth has put out their music is evidence of their greatness.
We all know Mikael is the creative engine behind Opeth. For the rest of the band members - as long as they can breath, I trust in Mikaels judgement of character and ability to choose people as replacements to keep the band together. Most bands experience changes. Sure, I was upset when Lopez left the band. Everytime I listen to Deliverence I hear and feel his greatness and his personal touch. Lopez can't be duplicated, nor can Peter, But they can be replaced. Yes there will be differences in their sound, some subtle and some obvious, as the new members bring their touch and feel to the music. But I have a difficult time believing that whatever Mikael writes will somehow not be "Opethian". I never considered any of the Opeth band members the #1 greatest in their respective playing positions. But as a unit, as a band, I find their sound unrivaled.
If Opeth doesn't work for you anymore, move on. But anybody who knows anything about music cannot deny the level of genious Opeth brings to the metal genre. My wife who is not a metal fan 100% can hear the talent in Opeth. The last time I saw Opeth play live was with Axenrot. It was still 100% Opeth, as again, I feel it's the combination of Mikaels writing ability and the bands ability to play the music as a group that is Opeth. I've heard much better guitar solos, bass solos and drum solos on an individual basis than what I've heard in Opeth's music. But the consistancy of Opeth and the music they put out as a group is not equalled in my eyes (more importantly in my ears).