Presonus have announced that their new firmware update to the RM (rack mount) series will allow you to chain two together to give you up to 64 channels together with bussing for a higher channel count, controllable via StudioLive CS19AI or UC Surface.
Currently the firmware update is running as a public beta, but will be done in around 30 days - so they are pretty close.
- See more at: http://blog.presonus.com/index.php/2015/12/21/beta-testers-needed-for-studiolive-rm-mixer-cascading-available-now/#sthash.bvHdZ892.dpuf
NAMM 2016 Kit:
Tascam DR-70D 4 Channel recorders