'retrofit hasn;t really been an issue since 120 rears... we went to 126 without evena grumble, and then 130 was a shoe-in - 135, inevitable... IMO

the TISO stuff looks trick, a lot will depend on the chain... but without going to a wider rear, fitting it all on the current freehub meaning way tighter spacing, of course.
This might all be nicely achieveable in a shop, but take it out on the road, on a 100 miles wet ride and things will change.
ever notice how quickly shifting gets more notchy and less positive as the chain gets dirty, dry or mucked from the lube picking up moisture and getting caked up?
Right now the one thing I notice about 10 spd is that caking on the chain, or dried crud, really degrades shifting quite a bit - hence my move to WD cleaning every other ride (when dry) and no 'lube' - I use WD for shortterm lubing with less chance of the chain getting caked with crud. Right now I give the chain a quick blast of WD almost every ride, quick solid wipe and everything runs great, every ride.
With the precision spacing needed for 12 spd on a 130, I would expect shifting to degrade even faster and be more evident.
Then there's the question of materials engineering and the inevitable cost of the materials and precision manufacturing, and then cog/chain longevity. Prolly less of a concern for the 'pro' scene and the small element who find a $250 to $500 cassette and a $200 chain, reasonable.
THen when you do that to the rear, the crankset/chainrings will certainly have to be re-engineered... $1K+ for a basic double ???
Would the market be big enough?
certainly would produce some trickle-down
IMO 135 offers a broad move to the entire marketplace. More space, less problems in giveing a broad range of 'Ace-Ultegra-105' type gruppos, and another reason for all of us to drop more dosh on a new frame, and of course the new wheelset and then all the goodies to make it a garagedoor photo-op.