At one point, the MK6 (full quad) and MK7 (NM full quad) were both under development.  The MK7 has since been released, but no word on the MK6.  Is the project DOA or is there still potential for a future release?

I want 2 know about the mk6 also

Better hurry up before bcm releases one, lol

BCMs looks gooooooood

Interesting factoid: the MK7 with an aluminum barrel nut and no weights (including the sling swivel bar) weighs LESS than the DD RIS II for the M4A1.  Both rails are between 12" and 13" (12.70" and 12.25" respectively.)  The MK7 is 17.2 oz, while the RIS II is 17.7 oz (of course, it does have the ability to split in order to mount the M203, which the MK7 does not.)  

Now, Bill Geissele said that the MK7 is derived from the MK6 and mentioned something about aluminum being "left on".  So, imagine taking a MK7 and adding the lightening cuts seen on the top of most SMRs and on the 3/6/9 pic on the MK4.  Not sure how much it would take off, but I would like to find out.

I think it should look exactly like this. If somebody wants lighter weight, there's other options.

That's already available as the MK7 (though, over 20 oz with the sling swivel bar and supplied steel barrel nut.)  Buy an aluminum barrel nut and lose (or cut down) the sling swivel bar to get down to the 17.2 oz I mentioned above.

Their SMRs are plenty tough and have lightening cuts, so I'd prefer a MK6 with them, too.  To each their own.