If its not mounts - as that would be a mechanic released free, and they are not ready for that - and all DLCs are out between Sept. 3 (release of Blood and Sand) and New Years…
… then maybe its stables? And some rider outfits? Animal skins… horses with saddles, etc.
Im going with Stables for the new building pieces… what else could it be.
Granted, Blood and Sand = Arena, and I totally didn’t see that coming, (but very logical)
Hoping for caravans (slow moving trade caravans) with carts (camels, elephants, rhinos). Stables would be cool (maybe craft one’s own ‘custom’ pet taming pen).
Animal trainer NPC and Caravan driver npc would be cool, too.
I don’t think we need faster travel, but not opposed to mounts. Chariot combat (archers/javelins) would be cool, but I’m not holding my breath for it (highly unlikely).
Wattle and daub mud housing would be cool building additions. Or even something more Adobe (mud bricks) or animal skin tents (small and large) for sandstorm protection (when you aren’t high enough level for a steel mask).