Yeah, AMD will eventually create more powerful APU's. Kaveri is coming later this year. We don't know anything about Carrizo (Kaveri's successor) other than the fact it'll be using Excavator cores. That won't arrive until 2015.
Since Kaveri's iGPU will (supposedly) be as powerful as the DDR3 variant of the HD 7750, Excavator might be as powerful as an HD 7770, probably even stronger. iGPU's won't be replacing mid-tier discreet cards for years to come, however. Performance will get better, but the biggest drawback to the iGPU's is their reliance on system memory for bandwidth, and that bandwidth is held back due to DDR3.
So in the future with DDR4, or perhaps even soldered BGA packages of APU's which have GDDR5 soldered to the board, we won't see any massive jumps any time soon. Of course, the IMC wouldn't be able to run DDR3/DDR4 and GDDR5 at the same time -- it'd be one or the other. That's another thing to consider.