Hehe. Well, I can give you my tentative list, but it is subject to change. 
I won’t commit to a finish until I actually see it on a prototype keyboard and can take photos of it to share.
These are the powder finishes:
K2 White with a subtle texture.
Aperture The most popular finish from the Heavy-6. Hammer tone silvery gray.
VHS A new finish, textured white and gray that creates an overall light gray impression. This is specifically designed to pair with my forthcomig After-School 1992 keyset, but goes well with tons of sets, especially light-colored ones. See image below. I love, love, love this finish.
Retro Refrigerator will be back! This may be matte or gloss, depending on test results, but I’m shooting to bring back the original glossy version. We’re using a special new process for treating the parts before powder-coating, which I hope will make the reject rate much lower on this tricky finish and therefore make it feasible again.
Astrophysical This deep purple with silver flecks is also returning, by popular demand.
Palm Desert This finish looks a lot like desert sand, textured light tan with medium-brown flecks in it. A great pairing with Chocolatier, or SA 1976, Galaxy Class, etc. I’m also currently working with @sour on an Arabic sublegend keyset that should pair well with this.
I’m also trying to offer Tactical Black, a black Type III (hard) anodized finish and/or Aerospace (clear Type II), but my current plan is to have the Mark IIs made entirely in the USA (for purposes of being able to do in-person quality control), and anodizing is hard here to source because environmental regulation has put most out of business in the past 10-20 years, or so it is said at least. Choice of vendors is therefore usually small, and finding one that can make something up to my cosmetic standards is therefore not assured. I’m getting samples from an anodizer that has been recommended to me highly, however, and will decide based on that.
I’m also thinking of offering a limited-edition solid brass version with a very unusual, experimental finish.