If the motherboard manufacturer used the right chipset lanes for the M.2 slots, yes. You will have to do some digging to determine that. The Z170 chipset offers 26 PCIe 3.0 lanes. Previous chipsets had both less lanes, and only 2.0 lanes from the chipset. So this is something thats new with the Z170.
There literally could be a motherboard now with 3 SSD's in M.2 4x slots (32GB each), all in a RAID 0.
What I am not sure about yet is if the six SATA III ports controlled by the CPU which we already know can be in a raid 0, can all be in a single raid 0 array with the M.2 slots. If they can be, you could potentially have 6 SATA III SSD's + 3 M.2 SSD's all in a single raid 0 array.
It is the Intel RST driver that is facilitating this. I haven't had time to go read all of the info that is out there on this yet, but I did read a review that said that 3 M.2 4x PCIe 3.0 lane slots could now exist, and be raid 0.