Maybe, the reason why they didn't announce anything is that it will be a Force Friday item? Much like the X-Wing starter 2.0 was for The Force Awakens?

Force Friday for X-wing was commercially dubious. It just doesn't sell well at big box store. Armada would be an even harder product to move.

That being said, SWM 20 could be hidden behind spoilers if TRY was given enough advance notice and could figure out a way to keep the playtestable stuff innocuous.

The one thing i took away from playing 40k for so long: " hope is the first step on the road to disappointment"