It's no secret that Samsung has had some issues with its big.Little processors. Either the two clusters weren't migrating as well as they should have, which ended up making for a jaggy experience, or it would overheat more easily. The last issue is also why Samsung is saying they can't enable the full 8-core performance in the Galaxy S4 and Note 3 with a software patch.
According to them, doing so would increase the heat and power consumption of the device, and it wouldn't be worth it. So it looks like the big.Little processor will be used as originally intended, by switching between the two CPU clusters, depending on the task at hand.
To me, it sounds like a good idea to fix the switching between the 2 clusters, first. If that's not working properly as it is, then having all of them working at the same time efficiently, sounds like an even harder thing to achieve. In theory at least, big.Little should be more efficient when using the Cortex A7 CPU, and also provide for higher performance when using the Cortex A15 one, but in practice that has proven harder than they thought, because there are hundreds of perhaps thousands of situations for which they need to optimize the system.
They need to know exactly in what type of apps to utilize Cortex A7, and in which to utilize the Cortex A15, and then they need to figure out when is the right time to switch between the 2 CPU clusters. On top of that, they also need to know when to keep just one or two cores of the 4 core clusters active, and when to activate all, just like with normal quad-core chips, so it doesn't use too much power.
Samsung is not going to give up big.Little yet, and I do believe we'll see a major improvement next year with the arrival of the Cortex A53/Cortex A57 big.Little chips, from both Samsung and Mediatek, because by then ARM itself should've optimized the big.Little system better in hardware, to work as intended. Still, I was hoping Samsung would be making their own quad-core non-big.Little CPU, just like Qualcomm, Apple, and Nvidia, because we can never have too much competition on the CPU side, and it would be interesting to see what they come up with.