I think it's affected by area as well as mine has risen again to 18k after dropping to £17250. Considering I bought it for £19600 2 1/2 years ago and put 20k on the clock I'm chuffed , 15 months time my balloon payment is £8650 and the car is mine .
All things suggest this is a temporary situation, likely to last another 18 months. So by the time your balloon payment is due, the value of your car is more than likely going to be back to normal levels.