So whats been released/teased so far, despite everyones wants and desires for AT-ATs, they are not feasable. In addition the mission objectives seem to be more company level skirmishes and firefights.
Speculation! Planetary assault expansion/campaign book.
I think it will bring:
Epic scale (1000-1500pt battles)
Huge vehicles (AT-ATs)
Fixed defences (golan defence turret, shield generator etc), orbital bombardment
Attacker/defender missions, new setups/battlefield conditions
Well.. thats what I think anyway