The upcoming Apple Watch Series 4 will feature a display resolution of 384x480p.
According to information found in watchOS 5, by 9to5Mac, the next generation 42mm Apple Watch will have a larger display resolution than the current Series 3. Currently the display is 312x390 pixels.
With increased PPI and resolution, the Watch Series 4's apps will be able to display more. This can be shown from the example image, from a modified Apple Watch simulator (with a 345 PPI).
As seen in recent leaks from Apple, the Series 4 of the Watch will feature a rounded display with reduced bezels, being able to display more content. Additionally, new Watch faces are to be added - at least one new digital and analogue face.
Similar to what happened with the iPhone X's display, developers will need to upscale their apps to work with the new Apple Watch.
Interesting fact - the original iPhone's screen resolution was only slightly bigger - at 375 x 667 pixels!