Not sure that a high quality nylon isn't going to be just as abrasion proof for practical purposes as nylon with the Dyneema grid. Getting into very light fabrics usually involves taking better care of the gear: not dropping the pack down chimneys, for example (like I foolishly used to do with 8-10 oz Cordura).
As for waterproofness, all we have to go on from T-H is, "Just the right amount of PU coating keeps it waterproof." Doesn't sound as though it is any more WP than what we have now; and unfortunately, my experience with PU coatings is that they degrade after a while. For a new, expensive lightweight pack fabric, something more is expected.
But for MYOG purposes, the suppleness of nylon, along with the tight stitch holes, make for much easier construction and effective sealing. I haven't seen this from any of the mylar laminates. So for me, the hunt for nylon with a better coating continues. Right now, I'm hunting balloon fabrics. Will see what develops. But yes, for a really super coating on a 100-200 denier high quality nylon, I would pay $30/yd.