I really don't see how Heritage is some vastly different and unexpected musical direction. Hints of it are all over Opeth's older works, especially Ghost Reveries and Watershed. I'm listening to Hours of Wealth right now, and the song reminds me a lot of Heritage and specifically Famine. A lot. There are parts even on Blackwater Park that sound like Heritage. Heritage is Mikael basically stripping out the metal and focusing largely on one or two aspects of his style.
All this is not to say that you have to like Heritage (though I do, a lot) or to imply something negative about you if you don't, because I don't believe in doing that. I just mean to say... it's not like they started playing fucking polka or house music or something. They definitely changed their music in a noticeable way, no question, but there's still a lot of elements in the new songs that are in older songs too, and besides, they've been foreshadowing this change for at least two albums.
And besides that, note my quip about In Absentia above. It was a joke, but there's some truth in it. I think the only reason no one ever really had that conversation is because In Absentia was pretty much universally heralded as an amazing album. If it had been less well-received... I would bet that plenty of people would say "I wish Steven had made a new project to do the metal stuff and kept Porcupine Tree the way it was."