This announcement is already a little bit older, but still relevant I think – Intel Optane can be used as RAM, and it is supposed to launch in 2018. This could potentially sidestep the LPDDR3 16GB RAM limit. And since 3DxPoint memory is non-volatile, it should reduce the standby battery usage essentially to zero. Also, with current Optane pricing, you can get 118 GB for €200, which would allow for a far greater amount of RAM without making the machines more expensive.
It remains to be seen if Optane is fast enough to completely replace DRAM (it probably isn't), but it could improve performance when used in tandem with traditional RAM.
http://www.tomshardware.com/news/intel-optane-dimms-timing-2018,35928.html