The big star of every I/O keynote is the latest version of Android. This year it will be Android 13, which is already being sent to developers. Expect to see more details about specific features, and previously-unknown updates.
The upcoming Google Pixel 6a handset might turn up at I/O. Google used the developer conference to unveil both the Pixel 3a and Pixel 3a XL back in 2019. The Pixel 4a, 4a 5G, and 5a were all announced in August or later; so perhaps an end-of-summer release is more likely for the Pixel 6a.
We’d like to see a successor to the high-end Pixel Buds, but with it being this close to the conference without leaks, it doesn’t look likely.
What is likely is lots of Wear OS news. The only smartwatch running the latest version of Wear OS came out last year. I/O would be a great time to announce more third-party Android smartwatches, and maybe even the Pixel Watch.