You have to hand it to Sony for their continued hardware innovation. The sensor technology that brought you the RX Camera series with stacked CMOS Technology; which is DRAM included as a middle layer along with signal processing makes it possible to capture data at tremendous pixel rates in the sensor block which leapfrogs competitors products.
That same 3-Layer stacked design is now unveiled on a cellphone geared sensor with a maximum performance at 1080p 1000fps and 4k 60fps. It is using the same buffer DRAM technology that will let you record for a limited time window and then save and process on your handset. Considering the speed quoted it is not out of the question to expect the Sony RX series of cameras to reach or exceed this level on upcoming iterations.