So in the pre-Disney canon the Empire was defeated at the Battle of Endor (or soon thereafter).
In the post-Disney canon it was defeated at the Battle of Jakku.
The ROTS teaser suggests we may return to Endor (or thereabouts). And to discover Rey's origins we'll need to return to Jakku.
The original Michael Arndt Episode VII treatment commissioned by Lucas had Rey and Luke treasure hunting for lost Jedi/Sith artifacts which then led to Vader's mask and Luke's saber appearing in TFA.
This early art for TFA shows the heroes taking the Falcon under water to seek out the Emperor's throne room which looks exactly like what we might be getting in TROS.
Oh man this really is looking like it will have George's fingerprints all over it but shot on 65mm film with mostly practical sets and real world locations.
Bring on the freaking ewoks, tighten up this whole Saga and show us how the FO is all a byproduct of Palpatine's final contingency to regain lost power.
For better or worse I'm never going to have this level of excitement for upcoming SW releases ever again and I'm freaking loving every minute of it.