Padme will be soon obviously, but not sure if she will be the next one. Tarkin is a very good guess since it would add to the Militaries line and give us an Imperial (since Stormtroopers are probably far off like Vader). Perhaps even generic or even specific other Imperial Officers. I know Piett and Veers would be good choices.
Palpatine is over do, but with only so many Sith to choose from, I think they will be spread out. Although we could get many Palpatine variants both scarred and non scarred Chancellor/Senator versions that could come with Sith robes.
I think another good alien like Greedo would go well with Jabba. I'd also like to see some more Jedi (please don't throw the tomatoes) like Ki-Adi-Muni, Saesee Tiin, and Agen Kolar (just to complete the Palpatine gang). I would be fine with a break after them.
Lando is another good option. Have a feeling it would be Jabba's palace Lando though. Which kinda sucks, but would make the most since with the current selction of figures to pose with him.