system
A chat on subreddit /r/pcmasterrace
human
It most certainly will. Single SATA SSDs will already be practically on that limit and since they will all go into the same controller (except for maybe some exotic setups) it wont even remotely approach an M.2 drive.
gpt
Someone hasn't tried it. I get double the transfer speed on X79 with  SATA3 Raid0, about 1 GB/s