Some ideas I'd love to see Hasbro tackle...
-Luke Skywalker: SA Luke Tatooine (finally), SA Hoth Luke Skywalker, and either SA Endor Luke Skywalker, or SA Death Star 2 Luke Skywalker.
-Leia Organa: SA Hoth Leia, SA Slave Leia, SA pregnant Leia Organa-Solo from Thrawn Trilogy
-Wookiee Legacy: SA mid-sized ROTS Wookie Warrior (bigger than Chewie, smaller than preview Wookiee, SA Chewbacca as Snoova, SA Wookiee Body Guard (Thrawn Trilogy)
-Rebel Soldiers: SA Fleet Trooper, SA Hoth Rebel Footsoldier, SA Endor Rebel Commando
-Imperial Military: SA Death Star Trooper (grey "Death Squad" Commander deco), SA black tuniced Imperial Officer, SA AT-ST Driver
The Evolutions line is probably one of my favorite items Hasbro's ever created... The concept delivers 3 figures for a fair price in general, and they're always pretty high quality (so far). I really feel Star Wars as a long, continuous story, lends itself well to the idea as well... For instance, I liked getting an NJO Luke in the Jedi Legacy set... I would've preferred a different Mandalorian in the Fett set, but it's still a cool figure and probably overall makes more sense (though the Mando guy from KOTOR would've been cooler, just on how his character looked).
For the "army building" aspect of things, Hasbro really has a winning format with Evolutions... I know I still buy the yellow Clone set if I see it... I mean, a Sandtrooper's always welcome, especially since I'm into non-film dioramas, and the Clone Pilot and Star Corps Clone are welcome additions to the army any time you can get them.
If they ever did that Rebel Evolutions set, I'd be sad... only at the thought of how I'd afford as many of them as I'd inevitably want. That'd be an incredible set if done right.