As Omega have said this won't be in this years moon landing LE I can't help but think that Omega want a slice of the waitlist pie, enjoyed by Rolex, Tudor BB GMT/BB58 and some of the Speedmaster LEs (ST1/2, Snoopy etc). I can see two possibilities here:
1. Omega will trickle out modern, 'heritage', non LE Moonwatches with the 321, step dial and applied logo at twice the price, in addition to the standard 861 Speedmaster.
2. It's Omegas solution to the moonwatch problem. We know Omega have said they have to keep on using the 861 in the moonwatch as putting an automatic coaxial in there will alter it too much from the handwound original. This makes sense from a historical (and marketing) perspective, but the issue from Omegas point of view is that it's keeping their flagship model at an entry level price point - you can't exactly increase the price in a short timeframe without altering something significantly.
So, is the new 321 just the 2019 version of the big black box, with loupe, medallion and Velcro strap. I.e. A way of Omega altering the regular Moonwatch significantly enough to dramatically increase the price of the regular production model, yet not so dramatically that it moves further away from the actual moonwatch.