I personally would favour a story in which we DO get to see Darth Vader as the real scourge of the Jedi. In ROTS he just whacked some kids, no biggy, kinda cowardlike, don't you think.
Anyway, I'm very glad it is going to be between ROTS and ANH since that is the only story that truly matters for SW. Any other is just EU and isn't truly SW.
I believe that we can expect Boba Fett and others to pop in from time to time, to further cement that bridge between PT and OT, perhaps then we get some more Wookiee scenes, perhaps we get to go down with some Bounty-Hunters as well, immersing ourselves in that brimming cup of SW-society that was so well made in ANH.
On the other hand, more Empire, more showing WHY the Rebellion exists in the first place.
So far, the PT hasn't shown us an Empire that is truly evil. Palpatine is a Sith, so he's a sworn enemy of the Jedi, he instigated a way, but that war was rather clean, just combat between combatants, we never saw any collateral damage, small or large scale.
I really really would like to see Palpatine's new order being executed throughout the galaxy.
Also, show us the development of ROTS machinery into that of the OT. Show how those RSD become ISD, V-Wings and JSF-2 turning into all types of Tie, how the ARC develops into the X-Wing and other S-foil equiped craft.
Because, with 6 movies, I still have that "What is so ******* bad about the Empire" sensation. Yes, the single act of utter cruelty is the destruction of Alderaan, apart from that, aren't the Empire just hunting down Terrorists (Rebels)?
On Tatooine, we see that there are Stormtroopers, but that could've been just the party send down from the SD.
On Endor, Ewoks still roam freely through the forest, they're not being hunt down, despite the planet being a key-part of the grand plan.
On Cloud City, Lando says the Empire has taken control of Cloud City, but that could just be to create chaos.
Thinking about that, the fact chaos erupts after Lando says it, seems to indicate fear for the Empire, but still.... only implied.
As a matter of fact, Lando is the only one who actually gives some sense of the Empire being oppressive, yet Cloud City is being tolerated by the Empire, so they're not THAT oppressive.
Anyway, regarding the TV-series, they do need to show a combination of things, adhering to what SW is about, because focusing on one aspect is too little to make for a good series. Too little to tell.