watchOS 7 was announced at the WWDC keynote yesterday, bringing sleep tracking, new watch faces, the ability to share watch faces, updates to Siri, handwashing reminders and tracking as well as improvements to Maps and more.
Apple is now dropping support for the Series 1 and Series 2 Apple Watch models. Series 2 was introduced in September 2016 and Series 1 was introduced along side the Series 3 in September 2017, it had the same internals as the Series 2 but wrapped in a Series 0 case. So it would make sense to drop both as they have the same S2 chip.
watchOS 7 is supporting Series 3, 4 and 5 and will be available later this year.