I thought about the Teddy issue earlier, and in the end didn't include it in my original list of unanswereds. I think I came down on whoever was looking after him during the battle. Though, with Harry as godfather, presumably he would have a hand/paw?
Also, was wondering about the main trio's jobs whilst cooking tea. What does the saviour of the wizarding world do afterwards, apart from the obvious with Ginny...
[I'll also be curious to see how they film the epilogue in three years time: new actors or aging make-up?]
Extrapolating, who's head at Hogwarts, for example, McGonagall? Was the Riddle "curse" lifted after his death and do Hogwarts now have DADA teachers lasting more than a year? Is Kingsley still Minister? Did Ollivander return to wand-making (though he'd likely have died by then anyway)? How many of the death eaters died, were captured etc? Draco seemed to be tolerated at Kings Cross, so how have they been accepted into society (Slytherin house seems to have been partially restored to equal favour, at least in some eyes)? Did Umbridge ever repent of her ways? Or Rita Skeeter?
However, despite all those questions, I think I'm happy not having that detail. Yes, it provides the options for another book/series/charity-publication(#), but in this instance I think adding detail would be unnecessary. We saw our ending, we just needed to wind-down slightly after the roller-coaster. Almost like a drug addict, here's a final hit before you hit the big "All was well." otherwise you'd be going back for more, and then some more, and more...
(#) If she wanted, JKR could do a very nice "where are they now" or "This is your life" style booklet for the next "Comic Relief" and still include loads of detail. The rest of the DA, Order, teachers and family: jobs and partners/families. The ministry, Hogwarts and Diagon Alley institutions' positions.