The main bottleneck of portable devices and even electric vehicles today are batteries. While the processing power is becoming greater every two years or so, and memory modules becoming more energy-efficient and faster, the only thing stagnating is the batteries.
The largest improvement in battery technology was the transition from Ni-MH to Li-Ion type of batteries and the latter one was further developed and brought to its limit. Now the only way to increase the battery capacity is to install a larger battery which is something we see in the latest Nokia phones but in phones of other manufacturers.
TechAltar did a nice video on this topic and from what I can see is that Li-Polimer or Ion batteries will be shipped with smartphones for the next few years, and slowly we’ll be transitioning to other similarly functioning batteries that will be more expensive to make and thus increase the price of smartphones and other products that will be using them.