With due respect to your own industry experience (which does admittedly give me pause as to your objectivity)...
It seems to me that a 5" mattress with superior technology could easily replace a 10" mattress of traditional manufacture. It wouldn't be the first time, either - who would have thought 10 years ago that the running shoe market would successfully be inundated with a bunch of "barefoot shoes?"
However, it might NOT be so easy to convince consumers that a 5" and 10" mattress are comparable, because for decades, that industry has been slapping layer upon layer of foam and pillow tops onto its mattresses to make the mattress LOOK good and justify increasingly higher margins.
I just ordered a mattress from Tuft & Needle because I want to give it a try myself. But I suspect that, if T&N want to be successful, they'll need to find analogies like the running shoe version (which is, admittedly flawed in that barefoot trainers aren't much cheaper than standard shoes) to explain how they can produce a 5" mattress that is as comfortable as a traditionally sized one.