Sounds great but not so sure that Aplle all be one of the first to adopt. Apple seems somewhat conservative and we will see many new batteries in the future.
Promising research project that is years from practical use, if ever. Absolutely 0% chance of being in gen 2 or even gen 3. As of now the Watch would have to be about 20mm thick, weigh 2x as much and still get only about 8 hours to work.