Musings on future Ponyville 3 packs...

[Sugar]

How about Rarity's parents with Sweetie Belle?  I'd love to see that.  They'd have to have those outfits, though... just to mortify my little Rarity figurine. 
 
And because I love old stuff, I'd love to see a sepia-toned set with Granny Smith as a filly  in her bonnet, her pioneer father (was he named?  I forget), and Stinking Rich the entrepreneur.
 
And since we're on the Apple clan, how 'bout Braeburn, Chief Thunderhooves, and Little Strongheart?
 
Because hey, if Kenner could make a whack of molds for the wee Jurassic Park metal dinos, go Hasbro for ponies! 

[Pinecone]

Fluttershy and the vet pony. I don't know who would be with them, though. Maybe a patient.

If they could make smaller ones without too much trouble, I'd want Snips, Snails, and Spike in a set.

[Bronley]

(most of these were probably already mentioned):

Villains:
Nightmare Moon
Discord
Chrysalis

Princesses:
Celestia
Luna
Cadance

Sparkle Family:
Twilight's Mom
Twilight's Dad
Shining Armor

Ponyville Services:
Mayor Mare
Nurse Redheart
Cheerilee

Exotic:
Daring Do
Mysterious Mare-Do-Well
Zecora