It's totally feasable that they think that the project (boards of canada) has run out of legs. They might have changed as people, music tastes, outlook on life, that it would be harder work to maintain the BoC theme they built, and would they even want to if it's not where their heart is anymore.
If they really have music in their blood, which I think they do then they'll just put their energy into another project but it might be wildly different than what we know, or they might be into totally new past times that they want to explore outside of music?
You have to end projects in their peak or at least when you start to become aware that there is a possibilty of a downturn in quality or personal interest in it, in order to maintain the legacy.
We all know of bands who we loved at their peak and they ruin it by plodding on and creating weak versions of themselves. I think BoC are self aware enough to know that the BoC legacy is way more important than them maintaining income or work. It's evident that this is not important to them otherwise they wouldn't be so elusive.
Good on them if there is any truth in this but remember, this a wild string of theories built up by yourselves with no solid basis. We can join dots and find really interesting links and coincidences in anything we see if we try hard enough but don't cement you train of thoughts into truth otherwise you'll be disappointed. But as I have always said, knock yourselves out, it's fun as hell and really interetsing to do, it's healthy if you keep it in context.
You could feel the bullshit