I'm assuming it is going to be a while. The unLace just came out, glow discs just came out, Vibram recently started doing the custom disc orders, and the O-Lace is being released in a few days. That is a ton on Vibrams plate and the most recent disc (O-Lace) hasn't even hit shelves yet.
I am sure they have plans for the next disc and are doing their share of diligent R&D but production has been tied up (and probably will continue to be, building up O-Lace stock, including future firms) with all the new releases and I'm sure development has been tied up with the multiple retoolings of the O-Lace.
My best guess (and I think this is still on the optimistic side) is we will receive a new disc to test at the beginning of the spring.
However, I hope I am wrong and we all receive tester discs tomorrow!
Edit: And I am hoping it's the Mobex or Ubex!