I think it's hard to say. There's a reason that folks have long sought "full range" main speakers. There are plenty of companies that build very large towers to achieve output down to 40Hz when much smaller speakers could get to 55Hz very comfortably (see Outlaw's diminuitive BLS for example and compare it to something like the Axiom M80, SVS MTS-01, Paradigm Studio 100, and a lot of other big towers).
Don't know, but that's apparently part of the point behind the H-PAS concept. The first link in your post noted that folks were impressed with the low frequency performance when the demo was in a 70,000SF room. That's a tall order for any speaker, including powered subs.
One of the arguments that THX made when they set 80Hz as the optimal crossover point was that anything higher started to become "directional" - you could start to identify where in the room the sub was. From that perspective, lower is better.
I don't know that H-PAS will be an industry revolution so large that it changes subwoofer design. Even with this, you can't get 40Hz out of a box that will fit in the palm of your hand. The arrival of flat panel TV's means there are still lots of people who want those tiny speakers, and those tiny speakers are still going to be lucky to get down to 80Hz. Plus there are plenty of people who really want that bass punch and will stack three or four large subs in a room to get it. There will always be big subs - especially from companies that specialize in subs (SVS, ED, and HSU Research).

At the end of the day, H-PAS is probably best suited to two-channel audio systems. In that regard, it's just like the RR2150 (which, not coincidentally, is what powered the prototypes at CEDIA last fall). It can and will also work well for home theaters, too, though. There are plenty of folks who want to run large front speakers because they prefer to not have a sub active when listening to music in stereo. Just looking at the folks here in the saloon, we've seen people doing that in their home theaters from day one. If these towers are small enough to blend into a living room or den (gotta think about WAF) and get down far enough to cover the low end for most music, there will be people to pursue it for just that reason. Personally, there's a corner of my brain that wonders what the following stereo setup would sound like: RR2150, BDP-83 (stock or, better yet, SE) and Outlaw H-PAS towers.