A couple of Rebels arcs featured Sabine’s mother and brother, Ursa and Tristan, and there’s always Fenn Rau.
The icy terrain seen in several of the trailer scenes also reminds me of Krownest, which first appeared in Star Wars Rebels Season 3 as the ancestral home of Clan Wren.
There are Rebels Mandalorians who definitely could have survived what happened to Mandalore, even if Sabine herself isn’t fated for a Mandalorian appearance… yet.
Rebels never established what happened to the Wrens aside from Sabine, other than that her father was rescued and at least temporarily reunited with his family.