Assuming they want to have 2 possible options for each type of unit...

January: Personnel Expansions

February: Jyn + Pathfinders

March: Krennic + Death Troopers

April: New Rebel Operative + Heavy

May: New Imperial Operative + Heavy

So maybe we will see something as early as June? I wouldn't mind seeing something earlier and they might opt to try and either have a Gencon release for the Clone Wars stuff or announce it there. Of course I could be completely wrong and come January they will announce something for them then for the April release. Or they could try to do a Heavy personnel expansion to give both factions something in April and strive to release Clone Wars stuff in May possibly to tie into May 4th, but knowing FFG's release schedule likely not.