"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
42mm Apple Watch Series 4 to Feature Resolution of 384x480
The current 42mm Apple Watch Series 3 model, for comparison, has a resolution of 312x390.
With the higher resolution (and increased PPI), Apple Watch Series 4 apps will be able to display more information at a higher resolution on the display, as shown in the example image below that were taken from a modified Apple Watch Simulator using a guesstimated PPI of 345.
As was seen in leaked marketing materials last week, the upcoming Apple Watch Series 4 models will feature at least one new watch face capable of displaying up to nine complications at one time.
Additional new watch faces could be included, and information taken from the beta suggests there will be new types of complications for Apple Watch apps to use.
Given the increase in resolution, third-party app developers will need to tweak their apps to work with the new Apple Watch Series 4 screen sizes.