I'll make a bit of an official statement here. It's totally fine if you're looking forward to a new expert pack and are frustrated by it taking so long between infinity expert and this new one. Feedback like that, as long as it's respectfully stated, is useful and absolutely helps us gauge how much interest there is in a new expert pack.
However, we will never give solid release dates on any packs or even promises that they will be released at all. Any statements we put out, official or unofficial, are simply our plans at the time, and those plans can change based on any number of factors, including ones that we can't discuss publicly. So it's possible that we could never give a good reason why a pack was delayed or canceled. I understand how this can be frustrating, but unfortunately it's simply the way this organization works.
We strive to be as open and public as possible, and to stick to our stated plans as much as we can, but sometimes it just doesn't work out.