Maybe guys with EVGA X99 FTW could try to use Silverstone M.2 Adapter if they use processor with 40 lanes.
 

 
SilverStone’s ECM20 is an adapter designed for users wanting to utilize or add speedy M.2 devices such as SSD onto their existing PC or motherboard. In addition to supporting one M.2 device (M key) to run via the super fast PCI-E interface at up to 32Gbps, a second M.2 slot (B key) is available for connecting to a SATA III port for added storage potential. For users looking to have the fastest data access speed on a desktop computer, the ECM20 is a must have.
 
http://www.silverstonetek.com/product.php?pid=575
 

 
I think EVGA should try and optimize BIOS maybe if need to support similar adapters without problem.
They could reach full speed if they work in PCI-E x8 slot and use lanes from CPU directly. With i7-5930K graphic card speed will stay x16 and dedicate sound card could be installed in small x4 slot connected with Chipset.

Guys who use SLI configuration usually have nothing against x8 speed and than could work together.
I don't know...M.2 is so fast and so good performance for money to ignore. I could not imagine self to invest now as something else than Samsung 950 PRO 512GB version for OS. Special because he could be used as long term option and removed in smaller case on smaller mATX board, no need for cables at all. You immediately move one SATA III cable and one SATA Power from PSU.

Yes, USB 3.1 example use 1 or 2 I think, or SATA Express if motherboard have, M.2 need 4 lanes Gen 3 for full speed.
Example this Silverstone card could be installed and in x4 slot but if he is connect with Chipset than M.2 will not offer max transfer speed.
For now all lanes from Chipset were Gen 2, Skylake change that and with Skylake-EP we should get perfect platform.
X99 is excellent but not perfect because Chipset is Gen 2. That's not big deal but sometimes could help.
If Skylake-EP show up with up to 48 lanes for some Processors with 20 more from Chipset same Gen 3 than people will have space to use CPU lanes only for GPU.
 
I think that SATA Express will be abandoned for 2-3 years completely and M.2 will stay and evolve. What you think about that.
I would not be surprise if soon some of premium motherboards show up without SATA Express. It;s good because ports could serve and as SATA III, but lack of SATA Express for me is not flaw at all.

The mistake Silverstone did was not come with a black bracket.  Most cases are black or in dark colors.  They did the right thing with the PCB but failed at the bracket.  

gtxjackbauer
The mistake Silverstone did was not come with a black bracket.  Most cases are black or in dark colors.  They did the right thing with the PCB but failed at the bracket.  

That's not big problem, bracket could be painted. 
Example if someone have i7-5960X or i7-5930K or next processors with 40 lanes he could install sound card,
this adapter and graphic card in EVGA X99 Micro 2 and to disable M.2 on Micro 2 board.
With X99 FTW is even easier because small slot could serve for dedicate sound card. 
GPU in first slot, M.2 adapter in 3rd slot.
 
Small slots are very important part of motherboards and it's sin build motherboard without them in any form factor.
Because no such good onboard sound as 90-100$ worth Sound Blaster Z. 
I made big mistake because I didn't paid extra 100 euro for i7-5930K because 40 lanes, when I had chance to buy i7-5930K for price of
i7-5820K. That would be pure gift.
Than I would not afraid installation PCI-E SSD or M.2 adapter on some boards, etc...