Since the devices are now reduced in size, all the fields which result in smaller dimentions are considered hot. For example, in wireless technology, it is a large attempt to decrease the power needed for a device to the lowest degree. There are also other areas for example the conversion from analog to digital or digiral to analog. But may be more than all of the above, there is a new field which works on mixed signal systems, i.e. boards or systems in which analog and digital are integrated. I think the new generation of future boards and systems will be mixed.