The original and 2nd gen Watch SE use aluminum bodies. There should be a chipset upgrade too. Apple’s September 9 event introduced the new Series

While the plastic Watch SE model is still in development, things are moving forward and the source states that it will see a potential launch next year. The shift to plastic has also posed some problems related to quality, but all of this is expected to move at a faster pace once Apple completes the transition to titanium for its premium models.

The Apple Watch Series 10 was everything we expected from the latest reports, but not much more. The more ambitious rumors of a big tenth-anniversary redesign didn’t come to fruition; instead, we got the more modest evolution into a thinner and lighter wearable with a noticeably larger screen.