"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Adds New 256 GB and 512 GB Flash Storage Options to iMac
Previously, the 21.5-inch iMac had not been available with dedicated flash storage options, only offering the standard 1 TB traditional hard drive and a $250 Fusion Drive option. Apple's Fusion Drive marries a 128 GB flash drive with a 1 TB traditional hard drive to seamlessly provide fast access to most-used files while also offering relatively cheap mass storage for the remainder of the user's storage needs. Those options remain available, but for those looking for an all-flash storage solution, Apple is now offering that in 256 and 512 GB capacities.
For the 27-inch iMac, Apple did previously offer an all-flash storage solution, but only as a 768 GB drive carrying a $900 upgrade fee. The 27-inch iMac is also available with 1 TB and 3 TB traditional hard drive options, with each of those also available in a Fusion Drive configuration. But with the addition of 256 GB and 512 GB flash options, Apple is now offering users who do not need massive amounts of storage the ability to maximize speed on their machines.