Before you trade in the BMW, if there's a CarMax near you, take it there for an appraisal. There is no obligation for you to buy from them, or even to sell your car to them, and the written offer is good for I believe 7 days.
They can get quite busy doing this service so give yourself ample time. But I think it's worth the effort...we got more from a Honda dealer for my father's CR-V (he was selling because he could no longer drive) I believe because of the pending CarMax written offer.
Speaking of which, consider selling it to a BMW dealer yourself. You might get more for it than if you traded it at a Nissan dealer.
Blue Ocean 2012 Leaf SV, lost that 1st bar at 34 months/26,435 miles. Lease returned 2 months later. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F.
Now driving a 2015 VW eGolf SEL.