You can read some of my theorizing in this previous post, but I have a little more information now that clears a few things up.
After talking with some folks at Camelbak it would appear the decision to discontinue the trizip was theirs alone. They cited the main reasons as cost (it was a pricy bag by imported standards) and competition with their other bag styles (such as the Motherlode). Viewing their current line up it appears as if they aiming for a very cohesive product line going forward, and in my view they did this well. The other bit of information I got was that to their knowledge there is no patent on the trizip opening itself, only the Futura Yoke that was also used for the Camelbak version. They also shied away from saying they "licensed" the design from MR, but insisted it was a collaboration.
Later, talking to Dana at Mystery Ranch, I got mostly the same story. He didn't sound as if he paid super close attention to the Camelbak spin off, but said he thought they'd priced it too close to the MR offering which meant by the time people had saved up for a CB they could save a little more and get a 3DAP or similar. Dana did use the term "license" for the design, but I'm sure this is just a fun semantics game that companies play. I didn't get the chance to ask him what he thought of the Nike version...
But as I predicted, it appears the Trizip is slowly gaining ground. I've found at least three new iterations; one from Timbuk2, one from Boreas, and a mysterious Diesel bag.
The Boreas seems to have been out for several years (here is a review from 2013, where I first noticed it). I'd briefly thought it had been discontinued but it appears to be back:
Slightly different lid geometry and they added some elastic to the inner collar, but mostly true to the original MR design.
The Timbuk2 version doesn't appear to be out yet, I just saw it over at the Carryology Winter OR Recap:
Unknown Timbuk2 pack
(photo credit: Carryology)
Also just found this on the EDC forums:
Looks a lot like an ASAP or Urban Assault from MR.
Keeping my eyes peeled for more now!