I guess it depends on what the framr designers decide to do - Santa Cruz seem very muvh on the 1x bandwagon and have removed front mech capability from the new Nomad. Will they do the same on the smaller bikes in the future?
QR axles are pretty much dead aren't they? They'll need some new axle standards soon though as the current ones seem to have been adopted (although chaging 20mm through axles to DH only now is annoying). 15mm and 142x12mm seems fairly common now. Bound to be changed soon.
Bottom brakets need sorting out although BB30 does seem to be winning.
Bar sizes? 31.8mm has been adopted by many which probably means that 35mm will get a huge push soon.
I actually think the dropper post has been good because seat post sizes have become standardised. Great for frame swappers. And good that it's killed silly sizes liked 30.0mm used by Kona who only Race Face and Thomson seemed to bother with.