I kind of understand this — there's something enjoyable about deep immersion in a series, esp. when you come across it years after it debuted and you have multiple volumes to read. Reaching the end of that and knowing you have another year to wait is sort of frustrating, esp. if that year produces only one more volume.
One aspect to this that occurred to me is that this really seems to favor established authors. A publisher isn't going to buy a trilogy from an unknown (cough), so this will only be possible for authors who are a known success.
I have to wonder if some writers who like to mix things up a bit (e.g., Steven Brust) will find this kind of idea a bit more stifling — ignore that idea you have for something new, and grind out X volumes of your Y series. I also wonder how this will work for longer series — bundle up three at a time? That becomes even more of a grind (and a longer interval between them); or does indicate that longer series may be on the way out in favor of more manageable binge sets.
I'll be curious to see how this trend plays out.
Impatience Has Its Reward: Books Are Rolled Out Faster
While the television industry has begun catering to impatient audiences by releasing entire series at once, the book business is upending its traditional timetable by encouraging a kind of binge reading, releasing new works by a single author at an accelerated pace.