I don't think so that AMD will have such plan in the near future.
The only compatible discrete graphics line for Dual Graphics with Kaveri APUs is R7 240/250 (Oland/Oland Pro).
However, you can install other higher range products like R7 250X/260/260X or even R9 cards as single discreet graphics (or even CrossFireX them).
Faster system memory e.g. 1866/2133/2400 is recommended if you want to install such cards.