I may be worng, but I really think that we're quite close to the point of diminishing returns for resolution for the 135 format. I mean, hell, we're already getting great 24" x 36" prints out of it, and shockingly good prints at the full width of an iPF8100. The latest batch not only outperform medium format film from back in the day, they're on a par with large format from not that long ago, and put a lot of Ansel Adams's work to shame.
In the online examples I've seen, you'd need to stick your nose against a door-sized print to tell the difference between the D800 and the 5DIII. The 5DIII images upscale nicely to the D800's native resolution, with less noise and almost as much detail.
Sure, we've got 20 megapickle digicams and could, in theory, scale those up to full frame...but we also know that those 20 megapickle digicams look like crap.
I'll make a prediction: there'll never be a pro-level DSLR 135-format with more than about 60 megapickles, and all it'll get you is a 30" x 40" print that compares well with a 24" x 36" print from a 5DIII or D800. The megapickle count will keep inching towards something in that range, but much more slowly...and, instead, manufacturers will put their improvements into actual camera features like Canon did with the 5DIII.
Damned few photographers need or can use even the full resolution of today's 135-format cameras, and those few who need even more have long since switched to medium format.