So we know Valter is getting a Grand Hero Battle soon so we can totally expect a Sacred Stone Banner to coincide with it. Chances are there are going to be two banners. One for Eirika and one for Ephraim. Maybe even they will be focus units too as both haven't been in focus for quite a while and their relationship with Valter. Let's just assume each banner will probably have 4 new units for a maximum of 8 new units from Sacred Stones.
In the potential banners, units I would like are
Tana(sword? We need more sword fliers...)
These are just units I would like to see in these banners if they exist in the future. I think everyone here agrees that a SS banner is coming. Right? Who would you like to see?