The new cases for Raspberry Pi B+ have already been announced. The new Model B+ sacrifices the physical compatibility with prev Model B due to additional ports and IO pins. This means that old cases that used to fit Model B no longer work with the new Model B+. 

Here is a roundup of new cases announced so far :

  1. Pibow Rainbow for RPi B+ from Pimoroni
  2. Pibow Coupé for RPi B+ from Pimoroni
  3. Pibow Ninja for RPi B+ from Pimoroni
  4. ModMyPi & Cyntech Raspberry Pi Case from ModMyPi
  5. Adafruit Pi Box Plus from Adafruit