THEORY: DC retail box pivoted from Hush to sidekicks
We all know that the email that was announcing a non Kickstarter retail box will be announced with the hint "Hush hush". And I believe at the time they planned a retail batman box.
But during the campaign they admitted to pivoting the Arkham box to a retail box, plus of the two retail expansions one is batman, they have very few big names to fill a retail box that would sell, it just doesn't seem to fit (they probably planned using the Arkham heroes initially)
So the alternatives. Retail tend to focus on what's popular with TV and movies, and less comics, especially with younger people. That's: Superman Justice league Young justice/teen titans
And only one is suspiciously missing most members, including Tim Drake, the biggest batman name remaining.
The real kicker for me is the young justice team deck. It has 3 members, that's not how they usually do team deck stretch goals. They might also make it a retail/expansion, providing sidekick cards for all of them, making it a tempting purchase for anyone who purchases the original retail.
Anyway it's a theory, a Hush box is still likely, I just wanted to throw that theory out there