When can we finally buy a smartwatch that can keep its (color) display ON during the entire day?
A Garmin memory-in-pixel eInk (MIP) watch? Lots of choices there, since about 2015. Modern versions (MIP not AMOLED, the category is getting confusing) last about 10 days on a charge.
Watches with color memory-in-pixel displays have existed since Pebble.
September 18, 2020. That's when Apple released their Watch Series 6, which has an always on color display, and enough battery to last all day.