I agree about the whole compatibility thing.
It’s a fairly safe bet that 135 offset frames will be around for quite a while as that’s currently the only way of fitting an Alfine or Rohloff (the latter have said that the potential market is too small – though they could change their minds).
170 is the next jump up and, although currently popular, seems to me to be a bit of a dead end. After all, if you’re going that wide, why not jump to 186/190 and give yourself the option of the wider, 5″ rubber?
Wheel dishing is all a function of the above.
Rim/tyre width is very much dependent on what type of riding you want to do – e.g. no need for 100mm if you’re not on soft sand or snow.
BB widths seemed to have settled at 100mm, though there are a couple of proprietary solutions popping up.
The “big boys” (Spesh/Trek) don’t currently seem to be driving a change of standards.
Remember the “half fat” solutions too. With Krampus-type 29+ already available and 27.5+ on the near horizon. I can see a lot of scope for the latter if they can be fitted into 29er frames.