Turning an H-bridge/motor off
The motor has a back EMF proportional to its speed. With this arrangement it couldn't have gotten to a speed where the back EMF was higher than 10V  - as the motor EMF approaches the supply voltage, the current falls to zero and no further acceleration is possible.

Once the bridge transistors are off, the EMF from the inductance of the windings generates an additional EMF as you describe, that allows the current to decay back into the supply until the current falls to zero. After that only the motor EMF remains, which drives no current since all the diodes are not forward biased and the transistors are off, so there is no net torque applied to the motor, and it'll just coast down under frictional and drive load. Both A and B will float somewhere between the supply rails, but remain with the same EMF between them.