There have been some hints that the Epic 40 HT package wasn't selling a lot, and it did disappear from the main pages of the US site a few months ago. The CDN view was not updated at the time so Epic 40 was still there.
AFAIK the Epic 40 is a wonderfully viable stereo music speaker (typically running without a sub), gets great reviews, and looks really good in the NRC tests -- but in the HT world where you have to have a sub anyways it doesn't offer much over the M3. Efficiency and power handling are about the same (naturally) so the only real benefit is flatter, smoother bass response.
The M22 actually seems to be a tiny bit more capable (spec-wise at least) of filling a large room -- if you measure the drivers 2 of the "5 1/2" drivers have almost exactly the same cone area as 1 of the "6 1/2" drivers -- so the main benefit of the M40s comes if you have a receiver which lets you set different crossover frequencies for mains vs. surround/center (ie an HK).
For HT customers I imagine the M22 is just an easier sell than the M40, for a mix of good and bad reasons. The good reason is that the M22 has "the M60 sound" which more of the Axiom buyers seem to prefer... the bad reason is that when you buy a tower speaker the full price is visible when you are making the decision, while with bookshelf speakers it's easy to fall into the "Oh nuts I need to get stands too" after ordering. You end up spending almost as much on M3s/M22s as on M40s once you factor in good stands but many of us don't think about stand cost when deciding which "Buy" button to push
If you look at the US site you'll see the M40 is still front and center in the "speakers" offerings, it's only the Epic 40 HT combination that has been taken off the site.