While things were pretty quiet on the SFF motherboard and case front at Computex this year, Mini-STX saw a decent number of announced boards and chassis.
According to the article, the M.2 is run off of the CPU directly and not via the PCH for faster M.2 performance. Hopefully that could mean adapters like the BPlus P4SM2 could be run at true PCIe x4 making use on a discrete GPU a possibility.
Oh nice, I've been toying with the idea of a mod using a STX board and a PCIe adapter from the M.2 slot for a discrete GPU + socketed CPU in a really small box.
Honestly if you had the BPlus adapter as well as a 90 degree riser to an ITX form factor you could essentially replicate the layout of the S4 mini but like extra mini.