It seems like the circumstances regarding the Empire in EP7 are leaning towards either A) the Empire is resurgent B) never really went away and now exists in a state of Cold War with the Republic, such as it is or C) the war never really ended. I'm fine with either, but would prefer something along the lines of B. Lucas intended for the Empire to be defeated at the end of ROTJ, as he intended the film to be the last at various points. He also intended for there to be as many as 6 more films beyond Jedi at one point, so it's uncertain if the Empire had been truly defeated. As has been pointed here and elsewhere, the Empire suffers a major defeat at Endor, but not a fatal one. You can look to what's happening in the Middle East right now (to a certain extent) and elsewhere in history to see how this plays out.
The Empire, militarily and politically, remains intact post Endor. The Emperor dissolved the senate, placed command of the galaxy in the hands of regional governors, and supported them with oppressive military that is only slightly represented at Endor. The entire Rebel fleet is present at Endor and suffers more extensive losses, one assumes, than the Imperial Fleet did. That same Rebel fleet is unlikely to have completely liberated the galaxy from an Imperial war machine that is at 97% capacity. No doubt some systems reject the Empire and there is a popular uprising. No doubt the Empire responds. No doubt someone, one of those governors or as yet unknown character (Max Von Sydow?) steps into Palpatine's shoes. The Rebels and Empire settle into a decades battle of attrition that sees a fledging new repbulic constantly under assault by an Empire that is simply too large and too powerful to truly go away.
The only flaw with this is that the Emperor was using the dark side of the force to control as many people as he could. He was influencing much of the Senate in AOTC and with the Jedi pretty much out of the way by the end of ROTS, his control was even more blatant.
With his death in ROTJ, the galaxy was freed from his control, hence the expanded ending scenes in the SE. There may be pockets of ready to follow imperial loyalists out there, but I doubt there'd be many of them.
I like seeing some of the images that have leaked, but I'll avoid spoilers until I see it with my oldest next December.