[quotemsg=18392157,0,723938]I'm still looking for the cable interface that will replace SATA3. M.2 looks great on paper, but you are limited to 1-2 per motherboard. I need minimum of three drives per computer (dual redundancy). All these new technologies look great, but it's too much of a mess to upgrade.[/quotemsg]
Finding a decent cabled solution is dicey, too. The SATA committee has stated there will be no new (faster) SATA spec, so 3 is it.
SATA Express was DOA, there are no SSDs, though you can find a bunch of ill-advised motherboards that have ports for it.
U.2 was not DOA, but it is dead now pretty much for usual consumer stuff, though it is growing fast in the enterprise. There is still only one client-centric U.2 SSD (Intel 750), but it is overpriced and the cabling is ugly, at best. Perhaps they will come out with the OcuLink cables, which are the "planned" slim U.2 cables, but I wouldn't hold my breath. There are RAID controllers for NVMe coming soon, but unless vendors make more consumer U.2 SSDs it will not help.