Although it's hard to verify from the image alone, we do expect the new model to feature a display that's 15 percent larger than the one on the Apple Watch Series 3, a change implemented through a reduction in the size of the bezels of the device.
The larger display sizes will provide more room on the screen for apps and allow more space for watch faces. Apple is expected to introduce at least one new watch face with support for up to nine complications.
The resolution of the new 40mm Apple Watch is still unknown, but data found within a beta version of watchOS 5 suggests the 44mm version will feature a resolution of 384x480, up from 312x390 in the current 42mm Apple Watch models.
Apple analyst Ming-Chi Kuo believes all Series 4 models will feature rear case ceramic, and potentially come with electrocardiography (ECG/EKG) functionality.
A leaked marketing image suggests the Apple Watch Series 4 will look similar to the Series 3, with no major design changes. As far as we know, that should ensure Apple Watch Series 4 models will continue to be compatible with existing Apple Watch bands.
Apple's "Gather Round" event will kick off today at 10:00 a.m. Pacific Time, with Apple planning to live stream the product unveiling on its event website and through the Events app on the Apple TV.
For those unable to watch, MacRumors will have live coverage both here on MacRumors.com and on our MacRumorsLive Twitter account, along with continuing coverage throughout the rest of September.